CBSE

Students can use Class 7 Science Curiosity Extra Questions and Chapter 11 Light Shadows and Reflections Extra Question Answer to prepare effectively at home.

Class 7 Science Chapter 11 Light Shadows and Reflections Extra Questions

Class 7 Science Chapter 11 Extra Questions on Light Shadows and Reflections

Light Shadows and Reflections Class 7 Very Short Question Answer

Question 1.
What image a pinhole camera gives?
Answer:
Upside down image

Question 2.
Where do lateral inversion occur?
Answer:
Not upside down. It occurs in an image torned by mirror.

Question 3.
What are non-luminous objects?
Answer:
It does not emits its own light. e.g: moon

Question 4.
Define luminous objects.
Answer:
They emit their own light. e.g: sun

Question 5.
Expand LED.
Answer:
LED: Light Emittind Diode

Question 6.
Light travels in a straight line. Is it true?
Answer:
Yes

Question 7.
Define shadow.
Answer:
A dark path, where no light reaches.

Question 8.
Light does not pass through it. What is it?
Answer:
An opaque object.

Question 9.
Define reflection of light.
Answer:
It refers to bouncing back of light from surface of an object.

Question 10.
Where are periscope used?
Answer:
In tanks, submarines ets.

Question 11.
Where is the image formed by a plane mirror?
Answer:
Behind the mirror

Question 12.
How many mirrors are used in Periscope?
Answer:
Two mirrors.

Question 13.
How does the light travel?
Answer:
The light travels along straight line.

Question 14.
You have three opaque strips with very small holes of different shapes as shown in Fig. If you obtain an image of the Sun on a wall through these holes, will the image formed by these holes be the same or different?
Answer:
The image of the sun obtained will be same through all the three types of holes.

Question 15.
What is light?
Answer:
Light is a form of energy which helps us to see the objects.

Question 16.
Give one example of natural source of light.
Answer:
Sun is a natural source of light.

Question 17.
Give the other name for light travels in a line.
Answer:
It is called rectlinear propagation of light.

Question 18.
How mirrors were mad in ancient times?
Answer:
By polishing metal or stone.

Light Shadows and Reflections Class 7 Short Question Answer

Question 1.
Give any two uses of a kaleidoscope.
Answer:
Kaliedoscope is used in:
(i) to see a different pattern every time
(ii) multiple images are formed in it.

Question 2.
Explain a pinhole camera.
Answer:
This device is used where light rays from an object pass through a pinhole to form an image on a screen.

Question 3.
How do you show that light travels in a straight lines?
Answer:
Beams of light from head lights of cars, scooters are seen by you. Light enters a room by a hole.

Question 4.
What is lateral inversion?
Answer:
When an image is formed by a mirror the left of the object appears on the right and the right appears on the left, this is known as lateral inversion.

Question 5.
Give characteristics of an image formed by a plane mirror.
Answer:
It produces upright virtual image, also image of same size as that of an object.
Distance of image formed on a mirror equals to distance of object in front of a mirror. This is laterally inverted.

Question 6.
Does light travels in straight line?
Answer:
Yes, light travels in straight line. Take a very long but hollow pipe. Bend the pipe. See an object in two pipes. We see candle flame through a straight pipe but not by a bend pipe. Hence, is shows lgiht travels in a straight line.

Question 7.
Define shadow. (V.Imp.)
Answer:
Light always travels in a straight line. But when an opaque object is kept in its path, light is blocked at all. A work patch where light does not reach is called a shadow. Opaque objects create darker shadow.

Question 8.
What does a pinhole camera give?
Answer:
It gives an upside down image leteral inversion occurs in image formed by a mirror, so it is not upside down too.

Question 9.
What are the factors that affect the size and shape of a shadow?
Answer:
The position of the light source, the distance between the object and the surface, and the shape of the object all influence the shadow’s size and shape.

Question 10.
What is reflection of light?
Answer:
Reflection of light is the bouncing back of light rays when they strike a surface.

Question 11.
What is a transparent material?
Answer:
A transparent material is one that allows most light to pass through it, enabling us to see clearly through it (e.g., clear glass).

Question 12.
What is a translucent material?
Answer:
A translucent material is one that allows some light to pass through it, but scatters the light, making objects behind it appear blurred (e.g., frosted glass).

Question 13.
What is an opaque material?
Answer:
An opaque material is one that does not allow any light to pass through it (e.g., wood, metal).

Question 14.
Write the characteristics of image formed by a plane mirror.
Answer:
The characteristics of image formed by plane mirror:
(a) The image formed is erect.
(b) The image is laterally inverted.
(c) The image is of same size as the object.
(d) The image is formed at the same distance as object is placed from mirror.

Question 15.
Briefly explain the following:
(a) Periscope
(b) Kaleidoscope
Answer:
(a) A periscope is an optical device that allows an observer to see objects that are not in their direct line of sight. It typically consists of a long tube with mirrors at each end set at a 45-degree angle.
(b) Kaleidoscope is used to make symmetric patterns. Fashion designers use this for making different patterns. It is also used
as a toy for children. The main use of periscopes is in submarines that remain under water.

Question 16.
What is shadow? How does the colour of an opaque object affects the colour of the shadow?
Answer:
A dark outline or patch formed by an opaque object that blocks light coming from a source of light is called shadow. The colour of an opaque object does not affect the colour of the shadow.

Question 17.
You have to cast the shadow of your pencil on the wall with the help of candle in a dark room. How can you obtain the shadow of same size, small size and big size of the same pencil.
Answer:
The shadow of the pencil will be small when the pencil is taken close to the wall and away from the candle.
The shadow will be big in size when the pencil is taken closer to the candle.
To get the same sized shadow as the pencil is, adjust the distance between the wall, pencil and candle at equal distances.

Question 18.
Can translucent and transparent objects create shadows?
Answer:
These create darker shadows of opaque objects. Lighter shadows are formed by translucent objects. Transparent object may form faint shadow too.

Question 19.
Why the word ambulance is written in an inverted form as  ?
Answer:
The word ‘AMBULANCE’ is written in an inverted (mirror) form on the front of an ambulance so that it appears correctly when seen in the rear-view mirror of a vehicle. This happens due to lateral inversion caused by the mirror.on the screen or surface behind the object.

Question 20.
A student covered a torch with red cellophane sheet to obtain red light. Using the red light she obtains a shadow of an opaque object. She repeats this activity with green and blue light. Will the colour of the light affect the Shadow? Explain.
Answer:
Changing the colour of light will not affect the shadow. This is due to the fact that shadow is a dark patch formed when the path of light is obstructed by an object which inhibits the light from reaching in the shadow region.

Question 21.
How is light reflected?
Answer:
Light reflection is defined as a change in light direction by a mirror. A mirror or even a shiny surface is responsible to change direction of light falling upon this too. e.g: I can see my face in a mirror, is due to reflection of light. Moreover both of a beam of light changes, when it falls on a mirror.

Question 22.
How are mirrors made?
Answer:
It is not clear when they were made but they were made by polishing metals or even shiny stones. Metals mirrors were out in use when glass mirrors came into use by people. Nowdays in Kerala state a metal surface mirror named Aranmuta Kannadi is made for hundred for years.

Question 23.
Define pinhole camera.
Answer:
This camera refers to a device where in light rays from an object pass by a minute/tiny hole. It form an image on the screen also. We take a cardboard. We make a hole in it. Lit a candle in room that is dim lighted. Put the light of candle in front of it. The light comes from a candle flame passes by a hole in cardboard or screen. It then makes an image of candle flame on screen also. Look at image. You see that at it is inverted (upside down).

Light Shadows and Reflections Class 7 Long Question Answer

Question 1.
Show how light gets reflected from a plane mirror with the help of an activity.
Answer:
Take a torch. Cover its glass with a chart paper which has three slits. Spread a sheet of chart paper on a smooth wooden board. Fix a plane mirror strip vertically on the chart paper. Now direct the beam of light on the mirror from the torch with slits. Place the torch in such a way that its light is seen along the chart paper on the board. Now adjust its position so that the light from the torch strikes the plane mirror at an angle. We will see that the mirror change the direction of light that falls on it. Now move the torch slightly to either side. We will see change in the direction of reflected light too. Look into the mirror along the direction of the reflected light. We see the slits in the mirror. This is the image of the slits. This activity shows how light gets reflected from a plane mirror.

Question 2.
given that light generally travels in a straight line, how do you explain the bending of light in phenomena like rainbows or when light passes through water?
Answer:
Although light usually travels straight, it bends when it passes from one material to another at an angle-this is called refraction. For example, when sunlight passes through raindrops, it bends inside the drops and splits into different colours, creating a rainbow. Similarly, light bends when it moves from air into water because water is denser, changing the light’s speed and direction.

Question 3.
With the help of an activity show that plane mirror forms laterally inverted image.
Answer:
Take a plane mirror. Stand in front of a plane mirror. Look at your image. Raise your left hand. It will find that in the mirror right appears left and left appears right. Such type of image is called laterally inverted. Now touch your right ear. It will appear right ear left and left ear in right side.

Note that in this image only sides are interchanged but the image does not appear upside.

Question 4.
What is the difference between an object and an image?
Answer:

Place a lighted candle in front of a plane mirror. Try to see the flame of the candle in the mirror. It appears as if a similar candle is placed behind the mirror. The candle, which appears behind the mirror, is the image of the candle formed by the mirror. The candle itself is the object.

Question 5.
How do you make some useful items?
Answer:
Periscope and Kaleidoscope are useful items. Light travels in a straight line but that is relected by the mirrors. The reflection from two mirrors make us able to see the objects which are not visible directly also. A periscope is useful in tanks and submarines. In a bunker, a soldier may see outside by it. An other useful item is Kaleidoscope in which multiple images are created.

Question 6.
A sheet of plywood, a piece of muslin cloth and that of a transparent glass, all of the same size and shape were placed at A one by one in the arrangement. Will the shadow be formed in each case. If yes, how will the shadow on the screen be different in each case? Give reasons for your answer.
Answer:
The sheet of plywood will form a dark patched shadow on the screen because it completely obstructs the path of light. Whereas the piece of muslin cloth will form a lighter shadow because it allows light to pass through it partially. The transparent glass will allow the ray of light to pass through it and hence does not form any shadow.

Light Shadows and Reflections Class 7 Case Based Questions

1. Read the following passage carefully and answer the questions that follow:
A group of students were experimenting with various materials in a dark room using a torch. They placed different objects-glass, wax paper, and a thick cardboard-between the torch and a white screen to observe the shadow formed. They noticed that the cardboard formed a dark shadow, the wax paper formed a faint shadow, and the glass barely showed any shadow. They concluded that the type of material greatly affects shadow formation.

(i) What type of material was the cardboard most likely made of?
(a) Transparent
(b) Translucent
(c) Opaque
(d) Luminous
Answer:
(c) Opaque

(ii) Which of the following best explains why the wax paper formed a faint shadow?
(a) It is a reflective material
(b) It is opaque and blocks all light
(c) It is translucent and allows partial light to pass
(d) It is luminous and emits its own light
Answer:
(c) It is translucent and allows partial light to pass

(iii) Why didn’t the glass form a noticeable shadow?
(a) It is a translucent material
(b) It reflects all light
(c) It is opaque
(d) It is transparent and allows light to pass fully
Answer:
(d) It is transparent and allows light to pass fully

(iv) What condition is not necessary for shadow formation?
(a) A source of light
(b) An opaque object
(c) A screen to capture the shadow
(d) A curved mirror
Answer:
(a) A source of light

2. Read the following passage carefully and answer the questions that follow:
The sun emits its own light but moon dies not. The moon only reflects light emitted by sun. In older times, there were several artificial sources of light as fire, light by a candle or a lantern lit by oil or gas also. So there are two kinds of objects as regards to light source. (a) luminous (b) non-luminous object.

(i) Name some sources of light.
Answer:
(a) Diya, (b) A lantern (c) A candle

(ii) Name two kinds of sources of light.
Answer:
(a) Luminous objects like Sun
(b) Non-luminous objeects like moon, diya, lantern etc.

(iii) In older times, what were light sources?
Answer:
Fire, lantern, candle etc.

Light Shadows and Reflections Class 7 Picture Based Questions

1. Look at the figure and answer the following questions:

(i) Identify the image given above.
(a) A kaleidoscope
(b) A periscope
(c) A pipe camera
(d) None of these
Answer:
(b) A periscope

(ii) In which shape, mirrors are placed to make it?
(a) T-shaped
(b) E- shaped
(c) Z-shaped
(d) Y- shaped
Answer:
(c) Z-shaped

(iii) Where are these cameras used?
Answer:
Periscopes are used in submarines, tanks, or by soldiers to see outside their bunkers. You may use it to look ahead when standing behind taller friends.

Light Shadows and Reflections Extra Questions for Practice

Multiple Choice Questions (MCQs):

Question 1.
Select the appropriate:
(a) sun emits light
(b) moon emits light
(c) candle emits light
(d) lantern emits light

Question 2.
LED refers to
(a) Light Engage Diode
(c) Lamp Emitting Diode
(b) Light Emitting a Die
(d) Light Emitting Diode

Question 3.
Do not point laser directly as it:
(a) may cause eye damage
(b) all of these
(c) cant bend at corners
(d) both (a) and (b)

Question 4.
Glass is a transparent object since light
(a) passes through it
(c) passes partially through it
(b) does not passes through it
(d) none of these

Question 5.
The light falls on a mirror
(a) it changes colour of image
(b) it changes direction of light
(c) it does not change direction of light
(d) all of these

Very Short Answer Type Questions:

Question 1.
Define: pinhole camera.

Question 2.
Write one use of Kaliedoscope.

Question 3.
Why do light travel in straight line?

Question 4.
What form shadows?.

Short Answer Type Questions:

Question 1.
Write uses of light.

Question 2.
Show Reflection of light with the help of figure.

Question 3.
Which objects make lighter shadows?

Question 4.
Classify the following as opaque, transparent and translucent objects- thick cloth, bird, glass, paper, cardbaord and tracing paper.

Question 5.
Can we see a candle glowing inside a room by a hole? Let us investigate. Give an activity too.

Question 6.
Name some sources of light.

Question 7.
Light cannot pass through an opaque object. Why it is so?

Question 8.
Show how light travels in straight line.

Question 9.
Draw a pinhole camera.

Question 10.
Construct a periscope. Label it also.

Long Answer Type Questions :

Question 1.
Discuss about non-luminous source of light.

Question 2.
How will you construct a pinhole camera? Show by an activity.

Question 3.
Compare periscope and kaleidoscope.

Students can use Class 7 Science Curiosity Extra Questions and Chapter 10 Life Processes in Plants Extra Question Answer to prepare effectively at home.

Class 7 Science Chapter 10 Life Processes in Plants Extra Questions

Class 7 Science Chapter 10 Extra Questions on Life Processes in Plants

Life Processes in Plants Class 7 Very Short Question Answer

Question 1.
What factors are essential for photosynthesis to take place?
Answer:
CO₂, sunlight, chlorophyll and water.

Question 2.
Why do plants need food?
Answer:
For growth and development.

Question 3.
Define photosynthesis in short words.
Answer:
Green plants → use CO₂ and water → to form glucose in presence of sunlight and chlorophyll too.

Question 4.
What food factories of a plant?
Answer:
Leaves (Green).

Question 5.
Name a chemical used to test the presence of starch in leaves.
Answer:
Iodine solution.

Question 6.
What transports H₂O and minerals from roots?
Answer:
Xylem

Question 7.
What do plants use in respiration?
Answer:
Oxygen and food.

Question 8.
What is function of caustic soda?
Answer:
It absorbs CO₂.

Question 9.
From where do we get food?
Answer:
From eating plants.

Question 10.
Plants store food in what form?
Answer:
In form of starch.

Question 11.
What are nutrients?
Answer:
The components of food that are necessary for our body are called nutrients.

Question 12.
What are stomata?
Answer:
Tiny pores present on the lower surface of the leaves that helps in exchange of gases are called stomata.

Question 13.
Whether food is made in all parts of a plant or only in certain parts?
Answer:
The food is made mainly in leaves and some other parts of the plants that contain chlorophyll.

Question 14.
What are the food factories of plants?
Answer:
Leaves are the food factories of plants.

Question 15.
Name the process by which plants prepare their own food.
Answer:
Photosynthesis

Question 16.
Name the pigment that makes leaves green.
Answer:
Chlorophyll

Question 17.
What is the function of chlorophyll?
Answer:
Chlorophyll captures the energy of sunlight.

Question 18.
What are the end products of photosynthesis?
Answer:
Glucose and oxygen

Question 19.
Name the gas used in photosynthesis.
Answer:
Carbon dioxide

Question 20.
Name the gas released in photosynthesis.
Answer:
Oxygen

Life Processes in Plants Class 7 Short Question Answer

Question 1.
What roles are played by CO₂ and O₂ gases in photosynthesis and respiration?
Answer:
Green plants use CO₂ and water in phototsynthesis to prepare food (glucose). This happens in presence of sunlight. On the contrary, plants respire by using oxygen to release CO₂ in it.

Question 2.
What are stomata? Where these occur? (V. Imp.)
Answer:
Stomata are tiny pore found in leaf surface (upper and lower also). They are meant for exchange of gases CO₂ and O₂ both in and out.

Question 3.
How do absorbtion of H₂O and minerals occur in plants?
Answer:
There are thin tubes present in stem, branch and leaves of plants. Minerals dissolved in water are transported to stem by xylem tissue.

Question 4.
What happens to food prepared by plants
Answer:
Plants prepare food by process of photosynthesis. Food prepared by plants is transported to all parts of a plant. Moreover, it occurs by tubeshaped structures called phloem. Transported food may also store in some plant parts like stem, leaf, root, seeds etc.

Question 5.
Write how do the plants respire? (Imp.)
Answer:
The plants taken in oxygen. They release carbon dioxide in turn of this. The food is broken down in presence of oxygen. The energy is released for plant growth and development. All parts of a plant do respire whether they are green or non-green. The word equation of respiration as:
Oxygen + Glucose → Water + Carbon dioxide + Energy ↑

Question 6.
What are contributions of R.H. Dastur about photosynthesis?
Answer:
Following are contributions of R.H. Dastur about photosynthesis:

• Studied process of photosynthesis at all.
• Served as Head of Botany at Royal Institute of Science in Bombay.
• Study on effects of water amount as well as the temperature in photosynthesis.
• Thoroughly examined the importance of temperature, water as well as colour of light in photosynthesis.

Question 7.
Explain process of photosynthesis in a nutshell.
Answer:
In a nutshell: Photosynthesis is a process of food formation in which carbon dioxide, water are taken by green leaves of a plant in sunlight and oxygen is released in air.
Carbohydrate (glucose) is formed in it. That serve as in start source of energy to plants. Glucose is changed to starch to be stored in leaves of a plant.

Question 8.
What is the role of air in preparation of food in plants? (Imp.)
Answer:
Air plays a main role in formation of food by plants. From air CO₂ and the water are taken to form food. Carbon dioxide present in air is necessary to prepare food by leaves. Water from air is used to prepare food by green plants. It occurs in sunlight. So plants take substance needed for photosynthesis, from their sorroundings. They also release oxygen for respiration.

Question 9.
Give an account of a woman scientist of India.
Answer:
A woman scientist of India. Kamala Sohonie (1911 to 1998)

• Contribution in area of respiration in the plants.
• She worked at Lady Harding Medical College, New Delhi.
• Worked at N.R.L. Coonoor.
• Remain Director of Royal Institute, Bombay now (Mumbai)
• Improvement in Nutritional value of plant foods.
• Work on sap of coconut palm (Neera a Nutrition drink to us)

Question 10.
Compare respiration to photosynthesis.
Answer:

Photosynthesis	Respiration
1. CO2 is taken in.	1. CO2 is given out in it.
2. O2 is given out.	2. O2 is taken in.
3. Foods is formed in this process.	3. Food is broken down in it.
4. Oxygen is released in the process of photosynthesis at all.	4. Energy is released during respiration at all.

Question 11.
Mention the roles of xylem and phloem.
Answer:
Xylem: These are tube like structures found in stem, branches, leaves. The minerals dissolved in water transported to stem by xylem.
Phloem: Food prepared by leaves is transported through phloem. It goes to all parts of body. The transported food can be stored in certain parts of plant like roots stems (potato) and seeds etc. Phloem transports glucose made in leaves to other parts of plant body.

Question 12.
How would you test for starch in a leaf? Explain. (V. Imp.)
Answer:
For test of starch in leaf we put a leaf in boiling water for 10 minutes for softening etc. Then dipped into a test tube that has alcohol in it. Then keep this test tube in boiling water until the leaf becomes colourless. Then take out leaf and put drops of iodine solution on it by a dropper. After minutes you may see that colour of leaf is changed to blue-black. It indicates the presence of starch in leaf.

Question 13.
A goat eats away all the leaves of a small plant (balsam). However, in a few days, new leaves could be seen sprouting in the plant again. How did the plant survive without leaves?
Answer:
During the process of photosynthesis, the plant takes water, carbon dioxide, and essential nutrients from the surroundings, converts them to energy or carbohydrates, and stores them. The plant managed to survive in the absence of leaves due to the energy stored in the plant in the form of starch.

Question 14.
How do plants obtain the raw materials for photosynthesis from the surroundings?
Answer:
Plants obtain the raw materials for photosynthesis from their surroundings in different ways. They absorb water through their roots from the soil, take in carbon dioxide from the air through stomata, and capture sunlight using the chlorophyll in their leaves.

Question 15.
Give a brief description of the process of synthesis of food in green plants.
Answer:
Green plants make their food using sunlight, carbon dioxide, and water. The chlorophyll in the leaves absorbs sunlight, while the plant takes in carbon dioxide from the air through small openings called stomata and water from the soil through the roots. Using sunlight’s energy, the plant combines carbon dioxide and water to produce glucose (food) and release oxygen as a by-product.

Question 16.
How do plants transport raw materials to the food factories of the plants?
Answer:
Plants transport raw materials to the leaves through different methods. Water is absorbed by the roots and carried to the leaves viaxylem vessels, while carbon dioxide enters the leaves through stomata. Nutrients from the soil are also transported with water. These materials are used by the leaves to make food through photosynthesis. The food prepared in the leaves are transported to other parts of the plant through another set of thin tube-like structure called the phloem.

Life Processes in Plants Class 7 Long Question Answer

Question 1.
What is the role of stomata in both photosynthesis and respiration?
Answer:
Stomata are tiny pores present on the lower surface of leaves. During photosynthesis, stomata allow carbon dioxide to enter the leaves. During respiration, they help in the exchange of gases oxygen comes in, and carbon dioxide goes out. Stomata are very important because they help the plant breathe and make food. Without them, the plant would not be able to take in the gases needed for life processes.

Question 2.
A student says that plants get their food directly from the soil. Explain why this statement is only partially correct. What is the complete process by which plants obtain their food?
Answer:
The statement is partially correct because plants do absorb essential nutrients and water from the soil through their roots, which are essential for growth. However, plants do not get their food directly from the soil in the form that they use it. The complete process involves photosynthesis, which occurs in the leaves. During photosynthesis, plants use sunlight, water absorbed from soil, and carbon dioxide from the air to produce glucose (sugar), their food. Therefore, while the soil provides necessary raw materials, plants manufacture their own food.

Question 3.
Where are useful information for plant growth, soil and agricultural practices recorded?
Answer:
There is an old proverb, “trees do not produce fruits and flowers merely because they are plants”. It is from Vriksha yugveda, an ancient Indian text. Various agricultural practices are helpful in improving growth of plants, their health and food production too. This knowledge has been explained on basis of practical experiences and the pattern at that line. Various farming practices are explained in this text from ancient times. Amid all this refers various methods of organic farming, the preparation of manures with help of water. Water is sprayed on manures. Water, barley, horsegrams, whether black or green etc.

Question 4.
Why is a leaf discolourised is starting in activity to test starch?
Answer:
In the starch test for leaves, a leaf is discoloured (or decolourised) at the beginning of the activity to remove chlorophyll, which is the green pigment in the leaf. This step is essential for the clear observation of the starch test results. To remove the green chlorophyll from the leaf so that any colour change due to iodine can be easily seen. Chlorophyll masks the blue-black colour that indicates the presence of starch. Boil the leaf in water for a minute: This kills the leaf and stops all chemical processes. Boil the leaf in alcohol (usually ethanol): This removes chlorophyll. The leaf turns pale or whitish. Rinse the leaf in warm water: This softens the brittle leaf after alcohol treatment.

Life Processes in Plants Class 7 Case Based Questions

1. Read the following passage carefully and answer the questions that follow:
During respiration plants take O₂ and release CO₂. The CO₂ is use in photosynthesis. In respiration energy is released too. The plants do not have special respiratory organs. In them gaseous exchange takes place by minute pores in leaf surfaces called stomata. You pass CO₂ in a flask having lime water. It will change in milky colour. So in process of respiration, plants take in O₂ and release CO₂. All parts of a plant whether green or non-green release CO₂ in respiration. During respiration, the glucose is broken down to CO₂, water and so energy is released to do work.
(i) What is respiration?
(a) Release of CO₂
(b) Release of Energy
(c) Release of H₂O
(d) All of these
Answer:
(d) All of these

(ii) Word equation for respiration is:
(a) Glucose + Oxygen → Water + Carbon dioxide + Energy
(b) Oxygen + H₂O arrow Glucose + H₂O + Oxygen
(c) Carbon dioxide + Water → Glucose + Water + Oxygen
(d) None of these
Answer:
(a) Glucose + Oxygen → Water + Carbon dioxide + Energy

(iii) The plants respire by stomata found in the:
(a) leaves
(b) roots
(c) flowers
(d) none of these
Answer:
(a) leaves

2. Read the following passage carefully and answer the questions that follow:
A science experiment was conducted using a balsam plant and coloured water. Over time, students observed the colour rising through the stem and reaching the leaves. The teacher explained this showed transport of water via xylem vessels. Similarly, the phloem transports food from leaves to other parts. These systems are part of a plant’s vascular tissue.

(i) What is the function of xylem in plants?
(a) Transport of food
(b) Transport of water
(c) Photosynthesis
(d) Exchange of gases
Answer:
(b) Transport of water

(ii) What does the phloem transport in plants?
(a) Water and minerals
(b) Only oxygen
(c) Food prepared by leaves
(d) Nutrients from soil
Answer:
(c) Food prepared by leaves

(iii) In which part of the plant does photosynthesis mainly occur?
(a) Roots
(b) Stems
(c) Flowers
(d) Leaves
Answer:
(d) Leaves

(iv) Which vascular tissues are responsible for transport in plants?
(a) Epidermis and guard cells
(b) Root hairs and stem
(c) Xylem and phloem
(d) Chloroplasts and mitochondria
Answer:
(c) Xylem and phloem

Life Processes in Plants Class 7 Picture Based Questions

1. Look at the figure and answer the following questions:

(i) Identify the figure:
Answer:
The diagram represents that sunlight is essential for photosynthesis.

(ii) From where does spotted plant get sunlight?
(a) From the sun
(a) and (b)
(b) From the air
(c) Both
(d) None of these
Answer:
(a) From the sun

(iii) Mention two conditions essential for formation of food by a plant.
(a) Sunlight, chlorophyll
(b) Oxygen, nitrogen
(c) Soil, glucose
(d) None of these
Answer:
(a) Sunlight, chlorophyll

Life Processes in Plants Extra Questions for Practice

Multiple Choice Questions (MCQs):

Question 1.
Photosynthesis occurs in
(a) green leaf
(b) root
(c) flower
(d) seed

Question 2.
Which of these elements is needed in addition to carbon, hydrogen, oxygen to make proteins?
(a) Nitrogen
(b) Calcium
(c) Iron
(d) Potassium

Question 3.
Necessary for photosynthesis:
(a) chlorophyll
(b) carbon dioxide
(c) Water
(d) All of these

Question 4.
Which of these are autotrophs?
(a) all plants
(b) all animals
(c) all insects
(d) all green plants

Question 5.
Water plus minerals transport occur by:
(a) xylem
(b) leaf
(c) flower
(d) epidermis

Question 6.
Which of these is not essential for photosynthesis
(a) carbon dioxide
(b) oxygen
(c) sunlgiht
(d) chlorophyll

Very Short Answer Type Questions:

Question 1.
Name a pores in leaves through which exchange of gases occur.

Question 2.
What is photosynthesis? Define in few words.

Question 3.
Name substance that is broken down in the body to obtain energy and to grow.

Question 4.
Name a structure that carries water and minerals from roots to leaves of a plant.

Short Answer Type Questions:

Question 1.
Do plants respire?

Question 2.
How is CO₂ released in respiration?

Question 3.
How do leaf exchange gases in photosynthesis?

Question 4.
Write a note in “Transport in plants”.

Question 5.
How do all plants get their food?

Question 6.
How is food formed in green plants?

Question 7.
Define breathing rate.

Question 8.
Give two differences between photosynthesis and respiration.

Question 9.
Give word equation for photosynthesis.

Question 10.
How does plants produce food?

Question 11.
What is so special about leaves that they can synthesize food but other parts of plants cannot?

Long Answer Type Questions:

Question 1.
Describe respiration in brief.

Question 2.
Take a test tube. Keep water and chlorophyll in it. Leave it open in the sunlight for 2-3 hours. Will photosynthesis occur in it or not? Explain briefly.

Question 3.
How would you test the presence of starch in green leaves?

Question 4.
How do plants make their food?

Question 5.
Show by help of a sketch that plants are the ultimate source of food.

Students can use Class 7 Science Curiosity Extra Questions and Chapter 9 Life Processes in Animals Extra Question Answer to prepare effectively at home.

Class 7 Science Chapter 9 Life Processes in Animals Extra Questions

Class 7 Science Chapter 9 Extra Questions on Life Processes in Animals

Life Processes in Animals Class 7 Very Short Question Answer

Question 1.
Where does journey of food begins?
Answer:
In mouth.

Question 2.
What are different parts of human alimentary canal?
Answer:
Mouth, buccal cavity oesophagus stomach and intestine.

Question 3.
What constitute human digestive system?
Answer:
Alimentary canal and its associated glands together constitute our digestive system.

Question 4.
What is the role of oesophagus?
Answer:
To push food ahead into stomach.

Question 5.
What are steps of respiration?
Answer:
The respiration is as following:
Glucose + Oxygen → Carbon dioxide + Water + Energy ↑

Question 6.
Name two grass eating animals.
Answer:
(a) Cow
(b) Buffalo

Question 7.
Do birds have teeth?
Answer:
No, they don’t have teeth.

Question 8.
Define breathing.
Answer:
It is defined as inhaling and exhaling of oxygen and carbon dioxide.

Question 9.
What is the role of a diaphragm?
Answer:
It plays roles in inhalation of oxygen and exhalation of carbon dioxide.

Question 10.
How do birds respire?
Answer:
By lungs.

Question 11.
Name the process by which energy is obtained by a living organism.
Answer:
Respiration.

Question 12.
What is the percentage of exhaled carbon dioxide during the breathing mechanism?
Answer:
Nearly 4-5%.

Question 13.
What is the length of the small intestine?
Answer:
About 6 meters.

Question 14.
Define the term egestion.
Ans:
The process of removal of faecal matter through the anus from time to time is called egestion.

Question 15.
What are ruminants?
Answer:
The animals in which partially digested food returns to the mouth and the animal chews it are called ruminants.

Question 16.
What is the role of the pancreas?
Answer:
The pancreas secrets pancreatic juice which is important for digestion process.

Question 17.
Which chemical would you select to test the presence of starch in the food item?
Answer:
Iodine solution

Question 18.
Name the organ that constitutes respiration in fish.
Answer:
Gills.

Question 19.
Where is water absorbed in the digestive system?
Answer:
Water is absorbed in the large intestine.

Life Processes in Animals Class 7 Short Question Answer

Question 1.
What is alimentary canal?
Answer:
Food is broken down in a long tube called alimentary canal. It starts with mouth and ends in anus.

Question 2.
What happens when chapati or rice break down into sugar?
Answer:
When saliva is mixed to rice or chapati, its digestive enzyme breaks starch into sugar.

Question 3.
Define digestion.
Answer:
It is break down of complex food components into simpler forms that can be absorbed by intestinal villi.

Question 4.
What is oesophagus?
Answer:
It is a tube that is long and flexible. It is called food pipe also. It does food move down into stomach by peristalsis.

Question 5.
Name three sources of digestive secretion into small intestine.
Answer:
(a) Inner lining of small intestine secrete digestive juices.
(b) Liver. It secretes bile juice
(c) Pancrease. It secretes pancreatic juice.

Question 6.
Give the function of diaphragm.
Answer:
It is a dome shaped structure, that move down wards in inhalation. It increase volume of chest cavity – Ribs move down and inwards – the diaphragm then moves upwards, push air out of lungs then.

Question 7.
How does fish respire?
Answer:
Fish respire by gills. Fish is aquatic animal. Gills are like slits having many gill filaments which have rich blood supply too. Blood absorb O₂ from water. CO₂ is given out by blood too.

Question 8.
How do amphibious respire?
Answer:
Frog is amphibian. It has gills in tadpole stage for respiration. Adult frog possesses lungs to breathe and respire, when in water frogs exchange O₂ and CO₂ by skin. This is an adaption to stay in water as well as on soil/land.

Question 9.
Mention functions of each:
(a) Liver
(b) Pancreas
(c) Villi
(d) Food pipe
Answer:
(a) Liver secretes bile juice. Bile juice helps in digestion of fats.
(b) Pancreas produces pancreatic juice that digests fats, proteins and carbohydrates at all.
(c) Villi are minute structures found in small intestine. They help in absorption of digested food to blood.
(d) Food pipe is esophagus, a long but flexible tube. It walls contract and relax to churn food. It is called peristalsis.

Question 10.
Give a short account of respiratory system.
Answer:
It has specific role of breathing as well as respiration. Respiratory system consists of lungs, trachea, wind pipe, nostrils, nasal passage etc. It starts with nostrils (through them air is inhated into lungs and air is also exhaled). Inhaled air now posses into nasal passage. Air is reached to lungs by means of trachea.

Question 11.
What is breathing rate? Give example.
Answer:
Number of times a person breathes in a minute is known as breathing rate. e.g., a normal breathing rate at rest is 12-24 times/ minute. Moreover this rate increases during heavy exercise at all.

Question 12.
Make two differences in Breathing and Respiration. (V.Imp.)
Answer:
Difference between Breathing and Respiration

Breathing	Respiration
1. It is a physical process.	1. It is a chemical process.
2. In it O2 is taken in but CO2 is given out.	2. Breakdown of foods occur to release energy too.

Question 13.
Explain rumination. Why cow is called a ruminant animal?
Answer:
Cow is grass eating animal. It partially chews grass. It swallow grass into their stomach. Partial digestion takes place here. The partially digested food is then returned to mouth for chewing slowly. This is known as rumination. So cow is called a ruminant animal.

Question 14.
How does birds eat as they don’t have teeth?
Answer:
Birds don’t have teeth, they have gizzard to chunk food. By contraction and relaxation, food is broken down with help of grit that are also swallowed by a bird too.

Question 15.
What processes occur in large intestine of humans?
Answer:
Most of the nutrients are absobed in small intestine. Then, undigested food moves to large intestine from small intestine. About 1.5 m length is observed of it. It is very smaller to small intestine. It is also called rectum. It is wider than small intestine. Water and some salts are absorbed by it. Most of water is absorbed by it. The undigested food becomes solid or semi solid. It is known as stool that is passed to outside by retal opening the anus. Stool is passed out by a process called egestion.

Question 16.
Why should we breathe through our nose?
Answer:
There are hairs present in our nasal passage. The hair entrap dust particles. These do not allow them to reach lungs. So, inhaled air becomes dust-free and clean. If, by chance these dust particles get passed, hair in our nasal cavity, sensory lining of the nasal cavity gets irritated. As a result we sneeze. The sneezing throws out these foreign dust particles from air inhaled at all.

Question 17.
Can you feel the breathing movements in your body?
Answer:
Yes, we feel breathing movements in our body. They can easily be felt by taking a deep breathe and keeping your palm on abdomen too. Movement of abdomen and expansion of our chest cavity can be felt with your palm.

Question 18.
What is peristalsis ? Explain in short.
Answer:
The wall of esophagus contract and relax to form a wave called peristalsis. It rushes food into stomach. Peristalsis refers to rhythmic contraction and relaxation of muscles in esophagus to push food forward.

Question 10.
Digestion in small intestine is carried out by help of liver and pancreas. Explain.
Answer:
Wall of intestine secretes juices. Liver secretes bile (stored in gallbladder). Pancreas secretes pancreatic juice that help to digest proteins, fats, and carbohydrates. The liver helps in the digestion of fats.

Life Processes in Animals Class 7 Long Question Answer

Question 1.
Explain with the help of a diagram, the process of digestion in human. Mention the role of different organs.
Answer:
Digestion in humans is the process of breaking down food into simpler substances that can be absorbed by the body. It involves several organs:
Mouth: Food is chewed and mixed with saliva which contains the enzyme amylase that starts the digestion of starch.
Oesophagus: Transports food to the stomach through a wave-like movement called peristalsis.
Stomach: Produces gastric juices (including pepsin and hydrochloric acid) that help break down proteins.
Small intestine: It is the main site for digestion and absorbtion. Enzymes from the pancreas and bile from the liver help digest fats, proteins and carbohydrates. The inner walls have villi that absorb nutrients into the blood.
Large intestine: Absorbs water from undigested food and forms solid waste.
Anus: Removes the waste materials from the body (egestion).

Question 2.
Describe the structure and function of the stomach and small intestine in the human digestive system.
Answer:
The stomach is a U-shaped muscular organ that temporarily stores food. It produces gastric juices containing hydrochloric acid and enzymes like pepsin that help digest protein. It also churns food to mix it with digestive juices.
The small intestine is a long, coiled tube where most of the digestion and absorption takes place. It receives bile from the liver and digestive enzymes from the pancreas. The walls of the small intestine are lined with villi which increase the surface area for absorbing nutrients into the blood.

Question 3.
What part of the digestive system is included in
(a) Killing bacteria
(b) Chewing of food
(c) Absorption of water
(d) Storage of undigested food
(e) Complete digestion of food
Answer:
(a) Stomach of human beings.
(b) Mouth – Saliva is mixed to it.
(c) Absorption of water occurs in large intestine/rectum.
(d) Undigested food is stored in rectum, last part of alimentary canal.
(e) Complete digestion of food occurs in small intestine. Here carbohydrates, fat, proteins are digested at all.

Question 4.
How do saliva help in digestion?
Answer:
Saliva is secreted in mouth. It is secreted by pairs of salivary glands. It digest starch into simple sugars. It digest rice that contains starch. So it helps in the chemical digestion of sugars. It is slippery so that food is mixed to it and pushes ahead to enter in food pipe.

Question 5.
How the food you eat gives energy?
Answer:
We eat food, it gives us energy to work, to walk etc. O₂ helps to break it into simple substances and release energy.
Glucose + Oxygen → H₂ O + CO₂ + Energy
So oxygen breaks down glucose to provide energy. Water and carbon dioxide are formed also. The whole process is called the respiration.

Question 6.
What is nutrition? Give its steps.
Answer:
Nutrition refers to intake of food, its digestion, absorption, assimilation and egestion. The food is taken in body by ingestion. In digestion, complex food is broken down to simpler substances. The digested nutrients are diffused into body fluids like blood. Using absorbed food to give energy is assimilation. Removal of undigested food from body is egestion.

Question 7.
How does absorption occur ?
Answer:
Digested food is absorbed in small intestine by villi. They are finger like projection in wall of small intestine. They increase surface area for food absorption. Each villus contain blood capillaries close to its surface. The absorbed food posses into blood via blood capillaries.

Question 8.
Differentiate between respiration and breathing.
Answer:

Feature	Breathing	Respiration
Types of process	Physical process	Chemical process
Involves	inhaling oxygen and exhaling carbon dioxide	Breaking down food (glucose) using oxygen to release energy.
Occurs in	Lungs and air passages	Cells throughout the body
Purpose	To bring in oxygen and remove carbon dioxide	To produce energy from body functions.
Requires energy	No	Yes
Produces	Only exchange of gases	Energy (ATP) carbon dioxide and water.
Control	Can be voluntary or involuntary	Completely involuntary.

Life Processes in Animals Class 7 Case Based Questions

1. Read the following passage carefully and answer the questions that follow:
The respiration is a process that occurs all the time i.e., during day and night. It is of 2 types aerobic (in the presence of oxygen) and anaerobic (in the absence of oxygen). Aerobic respiration occurs in both plants and animals. In both cases, intake of oxygen and release of water and carbon dioxide occur. Both oesophagus and trachea open into pharynx. It serves as a common passage for both food and air. The alveoli are richly supplied with blood vessels. O₂ present in air we breath in, goes into blood flowing in blood vessels of alveoli. CO₂ present in blood passes out of blood vessels into alveoli. Exchange of gases occur in alveoli of the lungs.

(i) Which of these is not true about respiration ?
(a) Redigest food
(b) Occurs only during day
(c) Utilizes oxygen exhales carbon dioxide
(d) None of these
Answer:
(b) Occurs only during day

(ii) Which of following organs serves as common passage for both food and air ?
(a) Pharynx
(b) Larynx
(c) Oesophagus
(d) Trachea
Answer:
(a) Pharynx

(iii) Where in respiratory system does oxygen from the air breathed in passes into the blood ?
(a) Trachea
(b) Bronchi
(c) Bronchioles
(d) Alveoli
Answer:
(c) Bronchioles

2. Read the following passage carefully and answer the questions that follow:
In an experiment, students placed boiled rice in two test tubes. In one tube, the rice was chewed before placing. Iodine was added to both. The unchewed rice turned blue-black, but the chewed one did not. This experiment showed that saliva breaks down starch into sugar, hence no starch was left to react with iodine in the second test tube.

(i) What does the blue-black colour in the test tube indicate?
(a) Presence of protein
(b) Presence of sugar
(c) Presence of starch
(d) Presence of fat
Answer:
(c) Presence of starch

(ii) Why didn’t the chewed rice turn blue-black with iodine?
(a) It had less iodine
(b) Saliva converted starch to sugar
(c) It contained protein
(d) It was overcooked
Answer:
(b) Saliva converted starch to sugar

(iii) Which enzyme in saliva helps break down starch?
(a) Lipase
(b) Pepsin
(c) Amylase
(d) Trypsin
Answer:
(c) Amylase

(iv) What is the conclusion of the experiment with chewed rice and iodine?
(a) Starch is produced in the mouth
(b) Chewing rice increases its starch
(c) Saliva begins digestion of starch
(d) Iodine turns red in presence of sugar
Answer:
(c) Saliva begins digestion of starch

Life Processes in Animals Class 7 Picture Based Questions

1. Look at the figure and answer the following questions:

(i) Label the diagram.
Answer:
1. Mouth
2. Windpipe
3. Liver
4. Stomach
5. Pancreas
6. Small intestine
7. Large intestine
8. Ractum
9. Anus.

(ii) Identify the figure:
(a) Alimentary canal of human
(b) Alimentary canal of women
(c) Both of these
(d) None of these
Answer:
(ii) – (a)

2. Look at the figure and answer the following questions:

(i) What does the above diagram show?:
(a) Movement of air
(b) Movement of food
(c) Both (a)-(b)
(d) None of these
Answer:
(b) Movement of food

(ii) Through which body part food swallowed to stomach?
(a) Oesophagus
(b) Wind pipe
(c) Liver
(d) None of these
Answer:
(a) Oesophagus

(iii) Oesophagus is also called:
(a) Wind pipe
(b) Stomach
(c) Food pipe
(d) None of these
Answer:
(c) Food pipe

Life Processes in Animals Extra Questions for Practice

Multiple Choice Questions (MCQs):

Question 1.
Liver and pancreas, release their secretions into:
(a) large intestine
(b) small intestine
(c) stomach
(d) oesophagus

Question 2.
Animal get energy from:
(a) food
(b) bases
(c) acids
(d) none of these

Question 3.
Largest gland in human body is:
(a) pancreas
(b) stomach
(c) kidney
(d) liver

Question 4.
Mechanical digestion occurs in:
(a) mouth
(b) oesophagus
(c) stomach
(d) intestine

Question 5.
Which of the following set of organs is involved in the digestion of food?
(a) Pancreas, liver and stomach
(b) Stomach, oesophagus and kidney
(c) Heart, pancreas and stomach
(d) Liver, pancreas and lungs

Question 6.
Stool is stored in:
(a) Rectum
(b) Small intestine
(c) Both (a) and (b)
(d) None of these

Question 7.
The air is exchanged in which part of the human respiratory system?
(a) Trachea
(b) Bronchi
(c) Larynx
(d) Alveoli

Question 8.
Which of these is a respiratory organ of fish?
(a) Nose
(b) Gills
(c) Lungs
(d) None of these

Very Short Answer Type Questions:

Question 1.
Why do organisms take food?

Question 2.
Do all animals have same mode of nutrition?

Question 3.
Name the secretion of the liver. Where is it stored?

Question 4.
What is effect of saliva on starch?

Question 5.
Give the function of mucus secreted by the stomach.

Question 6.
Where is bile stored?

Question 7.
Name the carbohydrate that can be digested by ruminants like cow, buffalo.

Question 8.
Can we survive on grass?

Short Answer Type Questions:

Question 1.
Why does fish die when fish is taken out of water?

Question 2.
When we hold breath for a few minutes, then release it. You have to breathe heavily after that. Why does it happen?

Question 3.
Write down functions of mucus and acid in stomach.

Question 4.
What are villi ? What are their functions?

Question 5.
How does fruit help in digestion?

Question 6.
How do we breathe?

Question 7.
Animals exhibit variations in alimentary canal. How?

Question 8.
Give word equation of the process of respiration in humans.

Question 9.
Birds do not have teeth. Why?

Question 10.
Small intestine receives digestive juices from three sources. What are they?

Long Answer Type Questions:

Question 1.
Getting energy from food we have two systems in our body to coordinate digestion of food. What are they? How do these help in digestion of food?

Question 2.
How does digestine system help in digestion and removal of wastes?

Question 3.
What are villi ? What their role in absorption of nutrients in small intestine?

Question 4.
When does a patient need drip of glucose? How is it useful to a patient?

Question 5.
Draw figures to show gaseous exchange in alveoli.

Students can use Class 7 Science Curiosity Extra Questions and Chapter 8 Measurement of Time and Motion Extra Question Answer to prepare effectively at home.

Class 7 Science Chapter 8 Measurement of Time and Motion Extra Questions

Class 7 Science Chapter 8 Extra Questions on Measurement of Time and Motion

Measurement of Time and Motion Class 7 Very Short Question Answer

Question 1.
What is formula for speed ?
Answer:
Speed = \(\frac{Distance}{Time}\)

Question 2.
Name the physical quantity that helps to identify which object moves faster or slower.
Answer:
Speed

Question 3.
What is speed?
Answer:
The distance covered by an object in a unit time is called its speed.

Question 4.
How did our ancestors find out the time of the day?
Answer:
Our ancestors could tell the approximate time of the day by observing at shadows.

Question 5.
What do you mean when you say that a car is moving with a speed of 50 kilometres per hour?
Answer:
It means that the car will cover 50 kilometres distance in one hour.

Question 6.
What are the most common devices used to measure time?
Answer:
Clocks or watches are the most commonly used time-measuring devices.

Question 7.
Give an example of periodic motion.
Answer:
A well-known example of periodic motion is the motion of a simple pendulum.

Question 8.
What is a bob?
Answer:
The metallic ball in simple pendulum is called bob.

Question 9.
What is the time period of a simple pendulum?
Answer:
The time taken by the pendulum to complete one oscillation is called its time period.

Question 10.
Name the devices used by our ancestors to measure the time before pendulum clocks.
Answer:
Sundials, water clocks, hourglass and candle clocks.

Question 11.
What is speedometer?
Answer:
The device which is used to record the speed directly in km/h in the vehicles is called speedometer.

Question 12.
What is simple pendulum?
Answer:
The simple device consists of a small metallic ball and a long thread is called simple pendulum.

Question 13.
What is the function of an odometer?
Answer:
Odometer is used to measure the distance travelled by the vehicle.

Question 14.
What is the common property of most of the clocks?
Answer:
Most clocks make use of some form of periodic motion.

Question 15.
What is the basic unit of time?
Answer:
Second

Measurement of Time and Motion Class 7 Short Question Answer

Question 1.
How was time measured when there were no clocks?
Answer:
Time was measured by sundials, water clocks and candle clocks in olden times.

Question 2.
Write two types of water clocks.
Answer:
(a) Water flowing out type.
(b) Floating bowl type.

Question 3.
Shadow based measurement of time was in which reference?
Answer:
It is written in Arthashastra by Kautilya.

Question 4.
Water clock was described in which book?
Answer:
In Sardulakarnavadana.

Question 5.
Which clocks were not accurate in ancient times?
Answer:
Water clocks etc.

Question 6.
State pendular motion.
Answer:
This periodic repeating its way after a fixed interval of time then.

Question 7.
A 24 hour long days has how much ghatis?
Answer:
60 equal ghatis.

Question 8.
Name some common clocks and watches.
Answer:
Quartz clock, writst watch, stop watch etc.

Question 9.
In a race, how can we tell, who is slow or fast?
Answer:
By measuring time by comparing races of different distances too.

Question 10.
State two kinds of motion in cities.
Answer:
(a) Uniform Linear Motion, and
(b) Non-uniform Linear Motion.

Question 11.
What are the factors on which the time period of a pendulum depends?
Answer:
The time period of a simple pendulum does not depend on the mass of the bob and nature of the material of the bob. It depends upon the length of the pendulum and acceleration due to gravity.

Question 12.
Convert 36 km/h into m/s.
Answer:
To convert 36 km/h into m/s;
Multiply by \(\frac{5}{18}\)
1 km = 1000 m and 1 hour = 3600 s
1 km / 1 hour = \(\frac{3600}{1000}\) = \(\frac{5}{18}\) km / h
36 km / h = 36 × \(\frac{5}{18}\) m / s = 10 m / s

Question 13.
What do you mean by average speed?
Answer:
The total distance covered by an object divided by the total time taken is called average speed. Average speed = Total distance covered/Total time taken

Question 14.
What is an oscillation?
Answer:
An oscillation is the movement of a pendulum from its one extreme position to the other extreme position and then back to the former position.

Question 15.
Show relationship between time, speed and distance. (Imp.)
Answer:
Speed is equal to distance covered divided by total time taken.
Speed = \(\frac{Distance covered}{Time taken}\)
We can also show it by formula:
Total distance covered = Speed × time
So,
Total time taken = \(\frac{Distance covered (in total)}{Speed}\)

Question 16.
What is Average Speed ? Explain in brief.
Answer:
Speed of an object = Total distance covered divided by total time taken too. An object may not have travelled at same speed during whole time or entire duration of time at all.
An object can move slower at sometimes. Hence we calculate average speed of an object. Therefore speed is in use in inspite of average speed also.

Question 17.
Why do we use average speeds in daily life a shown by train X and Y. Show it by table.
Answer:
Data compared of train X and Y

Table: The Distances Travelled by Two Trains in Equal time Intervals of ten minutes.
(i) An object → moves along straight line with constant speed Uniform Linear Motion.
(ii) An object → moves along straight line → speed changing → Non-uniform Linear Motion train Y.
Above data shown train X, Y showing two types of motions – train X, Y show these two.

Question 18.
Distinguish between Sundial and Water clocks.
Answer:
Difference between Sundial and Water clocks

Sundial	Water clocks
1. Measurement of the time by changing position of shadow of one object.	1. Water flow was used to measure time in/out of a vessel.
2. Cast by light of sun on a day time.	2. On vessel, these are markings for time to measure a all.

Question 19.
State what do you know about Ghatika yantra.
Answer:
(a) This came to notice by Aryabhatta.
(b) Mentioned by astronomical text later on also.
(c) Time is measured constantly by it at royal palaces.
(d) Each time bowl sank, drum was beaten or a gong was struck too.

Question 20.
Explain how Galileo contributed to the development of clocks.
Answer:
Once Galileo was sitting in a church. He noticed that a lamp suspended from the ceiling with chain was moving slowly from one side to other. He was surprised to find that his pulse beat the same number of times during the interval in which the lamp completed one oscillation. He found that a pendulum of a given length takes always the same time to complete one oscillation. This observation led to the development of pendulum clocks and other watches.

Measurement of Time and Motion Class 7 Long Question Answer

Question 1.
State how was time measured in olden days.
Answer:
People took help of natural events to measure time. These event happen at regular intervals of time. e.g., time interval between sun rise and sun set was called a day. Again time interval from one sun set to next sun rise was one night. Time interval between one new moon to next one was terned as one month time. Time taken to more earth one resolution of sun was a year too. Moreover, one second is time measured by available clocks/watches.

Question 2.
Explain the term “speed” in brief.
Answer:
Speed refers to time interval cover a maximum distance at all e.g., we cover 100 m in 5 minutes. S.I. unit of speed is meter per second. Hence the speed in distance covered by an object or body that is moving in a unit time. Cars, trains, aeroplanes move fast than bus, scooters etc.
When an object covers a distance (d) in time (t), it speed would be as
Speed = \(\frac{Distance (d)}{Time (t) taken}\)
Speed is actually an average speed of an object at all.

Question 3.
What do you know about clocks and watches ? Explain shortly.
Answer:
The electronic wrist watches and clocks are available in markets. They have crystals of quartz, a substance. The crystals vibrate fast too and also at accurate rate. These vibration are used to measure time. A quartz clock is more accurate in comparison to a pendulum clock at all. Stop clock and stop watches are mostly used in labs of schools and sports to measure time interval. They refer to improved form of wrist watches to measure time upto one tenth of a second (s).

Question 4.
Explain slow and fast motion.
Answer:
Observe the moving and rest position of an object. Suppose you sit near a window of a moving bus/train and are looking to outside. You see that the trees appear moving fast backwards. On the centuary, a man standing on road side, sees trees to appear stationary or fixed too. So we can conclude that motion is relative, everything in our universe is in motion too. So movement of an object or a body is fast or slow. We may move faster or slower at other way. The vehicles/trains move faster or slower too. Vehicles move on a road, you can see some are faster than others (slower).

Measurement of Time and Motion Class 7 Case Based Questions

1. Read the following passage carefully and answer the questions that follow:
A simple pendulum is made up of three parts as bob, string and rigid support. During rest position, it lies in mean position. If you move bob of a pendulum it begins the oscillatory motion then. The periodic motion repeats its path when fixed time interval is observed.

(i) What makes pendulum?
(a) A string
(b) A bob
(c) A rigid support
(d) All of these
Answer:
(d) All of these

(ii) When does oscillary motion start ?
(a) Move bob
(b) Move string
(c) Move support
(d) All of these
Answer:
(d) All of these

(iii) Mention features of a pendulum.
Answer:
(a) It has a bob.
(b) It possesses a swing.
(c) It also has a rigid support.
(iv) Define periodic motion of a pendulum.
Answer:
The repeat way/path in a fix interval of time of pendulum is called periodic motion..

2. Read the following passage carefully and answer the questions that follow:
During sports day, Raju ran 100 metres in 20 seconds while Priya completed the same in 25 seconds. Their teacher used this to explain the concept of speed, calculated as distance divided by time. Later, students plotted their performances on a graph and found that while Raju ran at a constant speed, Priya ran slower at the beginning and faster toward the end.

(i) What is the formula for speed?
(a) Speed = Distance × Time
(b) Speed = Time + Distance
(c) Speed = Distance ÷ Time
(d) Speed = Acceleration × Distance
Answer:
(c) Speed = Distance ÷ Time

(ii) If Raju runs 100 m in 20 seconds, what is his speed?
(a) 5 m/s
(b) 0.2 m/s
(c) 20 m / s
(d) 2 m / s
Answer:
(a) 5 m/s

(iii) A graph showing equal distances covered in equal intervals indicates:
(a) Irregular motion
(b) Increasing speed
(c) Uniform motion
(d) Decreasing time
Answer:
(c) Uniform motion

(iv) Which of the following indicates non- uniform motion?
(a) Steady speed
(b) Oscillation
(c) Unequal distances in equal time intervals
(d) Constant velocity
Answer:
(c) Unequal distances in equal time intervals

Measurement of Time and Motion Class 7 Picture Based Questions

1. Look at the picture and answer the following questions:

(i) Identify pictures (a), (b), and (c):
(a) The boys run in a race in straight track
(b) Quartz clock
(c) Sundial
(d) All of these
Answer:
(d) All of these

(ii) What is the smallest interval of time?
(a) Hour
(b) Minute
(c) Second
(d) All of these
Answer:
(c) Second

(iii) name the device you can see in Fig (b).
(a) Hourglass
(b) Water clock
(c) Candle clock
(d) Sundial
Answer:
(d) Sundial

2. Look at the picture and answer the following questions:

(i) What does the above figure show?
(a) A simple pendulum
(b) A watch bob
(c) Oscillation
(d) None of these
Answer:
(a) A simple pendulum

(ii) What is the metalic ball called in pendulum?
(a) Circle
(b) Ball
(c) Metal ball
(d) Bob
Answer:
(d) Bob

(iii) What type of motion the bob is doing?
(a) Uniform motion
(b) Non-uniform motion
(c) Linear motion
(d) None of these
Answer:
(b) Non-uniform motion

(iv) What is the time period of a simple pendulum?
Answer:
The time taken by the pendulum to complete one oscillation is called its time period.

Measurement of Time and Motion Extra Questions for Practice

Multiple Choice Questions (MCQs)

Question 1.
In olden times, the time was measured by:
(a) sundial
(b) water clocks
(c) hourglasses
(d) All of these

Question 2.
A simple pendulum has:
(a) one part
(b) two parts
(c) three parts
(d) four parts

Question 3.
S.I. Unit of Time is:
(a) m/s
(b) cm/s
(c) None of these
(d) Both (a) – (b)

Question 4.
Motion of trains between two stations is:
(a) Linear motion
(b) Oscillary motion
(c) Non-linear motion
(d) All of these

Question 5.
Find the speed shown below as correct:
(a) Speed = Time × Distance
(b) Speed = \(\frac{Distance}{Time}\)
(c) Speed = \(\frac{Time}{Distance}\)
(d) Speed = \(\frac{1}{\text { Distance × Time }}\)
Very Short Answer Type Questions:

Question 1.
Name three parts of a pendulum.

Question 2.
What is speed?

Question 3.
What do you mean by a clock?

Question 4.
Give one limitation of sundial.

Question 5.
What is meant by time period of a pendulum.

Question 6.
State one example of a body having uniform and periodic motion.

Question 7.
How was time measured in an hourglass?

Short Answer Type Questions:

Question 1.
What are slow and fast motions?

Question 2.
Write one use of stop watch.

Question 3.
When is an object said to be in non-linear motion?

Question 4.
On what principle modern electronic watches are based?

Question 5.
Give S.I. units of speed and time.

Question 6.
Give uses of:
(a) Odometer
(b) Pendulum and
(c) Speedometer

Question 7
Write any two points of difference in uniform and non-uniform motions.

Question 8.
State the relationship between speed, distance and time.

Question 9.
Briefly explain:
(a) Sundial
(b) Water clock
(c) Candle clock

Question 10.
By a diagrammatic figure show a simple pendulum.

Long Answer Type Questions:

Question 1.
Compare uniform and non-uniform speeds. Give two examples of each.

Question 2.
How was time measured in ancient times? Write briefly.

Question 3.
On what principle do modern watches work? Explain in short.

Question 4.
Define speed. How is speed measured?

Question 5.
Draw figures of watches and clocks used at home.

Students can use Class 7 Science Curiosity Extra Questions and Chapter 7 Heat Transfer in Nature Extra Question Answer to prepare effectively at home.

Class 7 Science Chapter 7 Heat Transfer in Nature Extra Questions

Class 7 Science Chapter 7 Extra Questions on Heat Transfer in Nature

Heat Transfer in Nature Class 7 Very Short Question Answer

Question 1.
What is smoke?
Answer:
Smoke refers “to a mixture of the hot gases and minute solid particles released when something burns”.

Question 2.
Define conduction in short.
Answer:
It refers to transfer of heat from hotter objects to colder parts; particles do not move their own places.

Question 3.
What are good conductors of heat?
Answer:
The materials which permit heat to pass through them very easily, e.g., iron, steel etc.

Question 4.
Why are houses made of hollow bricks?
Answer:
To keep warm during winter season.

Question 5.
What are convection currents?
Answer:
Land breeze, sea breeze.

Question 6.
Why do not utensils cool down?
Answer:
Due to radiating heat to its surroundings.

Question 7.
Give one use of bukhari in Himalayan regions.
Answer:
It keep us warm in rooms in winter season.

Question 8.
What is precipitation?
Answer:
First, water vapours rise up, then cool down and condense to make clouds that brings rain, hail or snow etc.

Question 9.
Why do we wear light coloured cotton clothes when it is hot?
Answer:
Light coloured cotton clothes give us a feeling of coolness by reflecting heat.

Question 10.
What do you mean by the transfer of heat?
Answer:
The heat flows from a hotter object to a colder object. This process is called transfer of heat.

Question 11.
How does heat transfer in water or air?
Answer:
By convection

Question 12.
How does heat transfer in solids?
Answer:
By conduction

Question 13.
Give two examples each of conductors and insulators of heat.
Answer:
Conductors-aluminium, iron. Insulators-plastic, wood.

Question 14.
What are conductors?
Answer:
Substances which allow heat to pass through them are called conductors.

Question 15.
What are insulators?
Answer:
Materials which do not allow heat to pass through them are called insulators.

Question 16.
What is sea breeze?
Answer:
The movement of air from the sea towards the land during daytime in coastal areas is called the sea breeze.

Question 17.
What is land breeze?
Answer:
The cool air from the land moves towards the sea at night in coastal areas is called land breeze.

Heat Transfer in Nature Class 7 Short Question Answer

Question 1.
Why are white clothes comfortable during summer?
Answer:
White clothes reflect most of the heat falling on them. Hence we feel more comfortable to wear white clothes in season of summer.

Question 2.
Distinguish between conduction and convection.
Answer:

Conduction	Convection
1. Heat transfers from hotter part of an object to cooler part.	1. Heat transfers in gases, liquids.
2. The particles do not move at all.	2. Actual movement of particles occur in it.

Question 3.
Explain briefly concevtion with the help of an example. (Imp.)
Answer:
An example of convection is boiling water in a pot. As the water at the bottom of the pot heats up, it becomes less dense and rises to the top. The cooler water at the top then moves down to take its place. This cycle continues, creating a convection current that evenly distributes heat throughout the water.

Question 4.
Compare sea breeze and land breeze.
Answer:
Comparison and sea breeze and land breeze:

Sea breeze	Land breeze
1. In day time in coastal areas, breeze mostly blow from sea to land.	1. The breeze blows from land to sea at night time.
2. Convection current.	2. Convection current.
3. Hotter and lighter air rise upwards, to take place of rising hot air in the day time.	3. Land loses heat at a faster rate to become cooler, rises up. it is observe land breeze during night.

Question 5.
Mention conditions for conduction of heat. Write examples of good conductors of heat. (V. Imp.)
Answer:
(a) Two objects must be in contact at all.
(b) Temperate of two objects must not be same.
Good conductors allow heat to pass through them e.g., the metals.
Bad conductor of heat do not permit heat energy to pass through them. They are also
called insulators e.g., air, water, wool, plastic, glass and cotton.

Question 6.
Tea or coffee kept in clay and porcelain cups stays hot longer. Why?
Answer:
Clay and porcelain are poor conductors of heat. They do not permit heat to pass through them very easily. Glass and wood are other examples.

Question 7.
Write about Varahamihira.
Answer:
Varahamihira was a scientist and astronomer. He too was a mathematician of 6 th century CE in Ujjain (M.P.). He was famous for giving a prediction about rainfall. The seasonal rainfall occured due to cloud formation, position of stars, patterns of wind, moon position. All these are natural processes.

Question 8.
What are Ice stupas ? Explain in brief.
Answer:
In Ladakh, people form layer after layer to develop a tall but cone like structure named ice stupas. In spring season when the streams dry up, heat from sun could not melt snow there on hills. Water sprayed into cold air to freeze.

Question 9.
To keep her soup warm, Paheli wrapped the container in which it was kept with a woollen cloth. Can she apply the same method to keep a glass of cold drink cool? Give reason for your answer.
Answer:
Yes, she can. The air trapped between the layers of wool is a poor conductor of heat. The trapped air prevents the flow of heat from surroundings to get inside the woollen layers and vice versa and hence prevents it from getting cool down or getting warm respectively.

Question 10.
What is ground water ?
Answer:
It is water that seeps through as well as then stored in the pose spaces of sediments as well as stored in openings of the rocks below earth surface at all.

Question 11.
Shopkeepers selling ice blocks usually cover them with jute sacks. Explain why.
Answer:
The layers of Jute traps the air in between the fibres. The trapped air prevents the flow of heat from surroundings to the ice and hence prevents it from melting.

Question 12.
Why do we wear dark-coloured clothes in winter season?
Answer:
Dark-coloured clothes absorb more heat, hence we wear dark coloured clothes in winter season. They remain comfortable also.

Question 13.
Water scarcity makes life difficult. Comment on it.
Answer:
Due to excessive use of water, it becomes a difficulty to our life. The people created innovative methods to conserve it by forming ice-stupas in hilly regions during winter season. Excessive extraction of grown water is caused by increasing population in India. The vegetation cover is also depleting. To control it aquifers are made.

Question 14.
Give uses of bad conductors of heat.
Answer:
(a) Handles of vessels in which we make food are made of wood. It is a bad conductor of heat. So, it does not get heated soon. Allow easy handling also.
(b) Jute or saw dust being in this category are used to cover ice to prevent melting at all.
(c) We wear woollen clothes in winter season. More spaces occur in wool fibres. They are filled with air. Wool and the air trapped in this keep us warm.

Question 15.
How do mud and wood help in keeping warm in houses ? Give a reason.
Answer:
Wood and mud are poor conductors of heat. In the upper regions of Himalayas (e.g., Mori block of Uttarakhand) has intensive cold climate. Here heavy snowfall takes place in winter season. All houses are made to stay warm in winter. Hence walls of houses are made of two layers of wood. In between two walls cow dung and mud is put to prevent heat losses. Thus houses are helpful to keep warm people there.

Question 16.
Distinguish between convection and radiatiton with their examples.(M.Imp.)
Answer:
Difference between convection and radiation:

Convection	Radiation
1. No actual movement of molecules.	1. Heat from fire reaches us.
2. Occurs in gases and liquids, primary mode of transfer of heat in liquids.	2. Heat transfers at fast rate than convection.
3. At bottom, water is heated, it moves upto top. Whole water gets warm then.	3. Black/dark coloured clothes reflects sun’s heat. So are more comfortable in winter.

Question 17.
How expansion of air on heating cause a balloon to rise up?
Answer:
Expansion of air on heating in sun, the baloon gets heated air of baloon on heating expands a baloon now becomes larger in volume. It occurs by convection.

Question 18.
What do you mean by conduction mode of transfer of heat energy?
Answer:
The process by which heat is transferred from hotter end to colder end of a metal is called conduction. In this process, molecules of the substance do not move but heat energy is transferred. In solids generally, the heat is transferred by the process of conduction.

Question 19.
Describe heating and cooling of land and water at different rates.
Answer:
It can be explained by sea and land breeze. In day time land gets heated at fast rate than water. Warm air rises upwards. Hence makes cooler air move from sea to land. It is sea breeze.
At night, reverse happens. Land cools faster than water as there is not sunlight. Air above sea is warm, it rises upwards. Now cooler air from land move towards sea to cause land breeze.

Question 20.
Conduction, convection and radiation work in bukhari. How? Explain in short with figure.
Answer:
In winter, bukhari keeps us and rooms warm too. It happens in upper regions of Himalaya. A bukhari is made of iron stove. In it we burn charcoal or wood. A long pipe remains attached to upper portion of heater. It function as a chimney. They chimney wents smoke out.
We may use bukhari to cook food. Its flat top, utensils are kept. So all these process of heat transfer are included in it. Moreover, this device is also useful to cook food as well as to warm the homes/houses. It keeps room warm.

Question 21.
Water is stored in sediments of rocks. Discuss.
Answer:
Water seeps in pore spaces of the sediments beneath surface as ground water. These underground layers both made of rocks can store water. It is done in aquifers. Extraction of the water occurs by digging wells. It can be done by boring drill wells to into aquifers. At different places or locations, a few meters to 100 meters beneath the ground, we may get water. This groundwater is not unlimited due to growing needs of people. Hence, extraction of ground water becomes a necessity to us.

Heat Transfer in Nature Class 7 Long Question Answer

Question 1.
Write the ways of transfer of heat. (V. Imp.)
Answer:
Transfer of heat takes place by any of following three methods. They are:
(i) By conduction
(ii) By convection and
(iii) By radiation

(i) The transfer of heat from a hotter to colder end of the object is conduction. It occurs in solids, gases and the liquids. It is fastest in solids.
(ii) Heat transfer by the mass movement of a liquid gas itself is convection. Heat transfer occurs by actual movement of molecules from a hot region to a colder region at all.
(iii) In it, heat transfer is faster than conduction or convention. Black body absorbs more heat than a white body.

Question 2.
What are good and bad conductors of heat? Give examples of each type.
Answer:
Good conductors permit heat to pass through them easily e.g., metals like steel, iron etc. So cooking utensils are made of metals. Bad conductor of heat is wood. It is poor conductor of heat that does not allow heat to pass through them easily e.g., wood. Fabric woolen is other example of it.

Question 3.
Compare conduction, convection and radiation.
Answer:
Comparison between conduction, convection and radiation:

Conduction	Convection	Radiation
1. Heat transfer from hotter part of one object to colder part.	1. Heat transfer in liquid and gas by it.	1. Heat travels from a place to other.
2. The particles do not move from their own position.	2. Actually particles move in it.	2. No medium is essential.
3. Example: metals.	3. Example: land breeze, sea breeze.	3. Example: sun’s energy.
4. Good conductors, insulators of heat.	4. Smoke rises up when something is burnt.	4. Sea water evaporates by it.

Question 4.
Draw water cycle by a word diagram.
Answer:

Question 5.
Show that water is a bad conductor of heat.
Answer:
Take a test tube. Now fill it half with the cold water. Now wrap a piece of ice in a copper wire gauze. Now you drop this into a test tube observe this. It sinks at bottom. Now hold top end of test tube by holder. Then heat it over a flame.
Inference: Water starts to boil soon. Ice not fully melted upto now. So we see that “heat is not transferred through water molecules”. Thus water is a poor conductor of heat.

Question 6.
Explain:
(a) Why wet clothes dry faster on a sunny day?
(b) Hollow brick is a poor conductor of heat. Why?
Answer:
(a) Wet clothes dry faster on a sunny day as the heat from sun is responsible for faster evaporation of water on a sunny day.
(b) Hollow bricks are poor conductors of heat since hollow bricks keep warm in the winter season but cool in the summer seasons. The air gets trapped in hollow bricks. The outer walls of houses are made from hollow bricks.

Question 7.
You are given a thick blanket and a combination of two thin blanket joined together. Which one of these two blankets will you choose?
Answer:
Suppose we are given the choice in winter of using either a thick blanket or two thin blankets joined together, then we select the blanket which is formed by the joining of two blankets because there would be layer of air in between the blankets. The air is poor conductor of heat. So this blanket gives more warmth.

Heat Transfer in Nature Class 7 Case Based Questions

1. Read the following passage carefully and answer the questions that follow:
Some people reside in coastal areas. They see heating, cooling of land and the water. But the rates of both are different. When the land is heated fast than water in a day. The result is warm air lying above land to rise. Now cooler air movement occurs from sea towards land. The phenomenon is known as sea breeze.

(i) What is sea breeze ?
(a) Cooler air moves from sea to land
(b) Heating cooling of land
(c) Rising of warm air above land
(d) None of these
Answer:
(a) Cooler air moves from sea to land

(ii) In the costal areas, windows of homes face the sea. It is due to:
(a) convection
(b) sea breeze
(c) heating of land
(d) cooling of sea
Answer:
(b) sea breeze

(iii) In hot place, the sea breeze gives comfort to people from heat due to:
(a) land heated in day
(b) warm air above land
(c) land breeze
(d) sea breeze
Answer:
(d) sea breeze

2. Read the following passage carefully and answer the questions that follow:
Modes of Heat Transfer in Daily Life
In a classroom experiment, students heated a metal rod with wax-attached pins and observed that the pins fell one by one starting from the heated end. In another experiment, coloured water in a beaker was heated from below, and the colour started rising and circulating. These demonstrated the different modes of heat transfer: conduction in solids and convection in liquids.
(i) What mode of heat transfer was demonstrated in the metal rod experiment?
(a) Conduction
(b) Convection
(c) Radiation
(d) Insulation
Answer:
(a) Conduction

(ii) What mode of heat transfer caused the coloured water to rise in the beaker?
(a) Radiation
(b) Convection
(c) Conduction
(d) Diffusion
Answer:
(b) Convection

(iii) Which material is the best conductor of heat among the following?
(a) Plastic
(b) Wood
(c) Copper
(d) Glass
Answer:
(c) Copper

(iv) What kind of heat transfer allows us to feel warmth from the sun even though it’s 150 million km away?
(a) Conduction
(b) Convection
(c) Radiation
(d) Expansion
Answer:
(c) Radiation

Heat Transfer in Nature Class 7 Picture Based Questions

1. Look at the picture and answer the following questions:

(i) Identify the picture:
(a) An aquifer
(b) Water cycle
(c) ungle
(d) None of these
Answer:
(a) An aquifer

(ii) What is an aquifer?
(a) Surface water seeping in soil
(b) Recharge pits
(c) Underground layers of rocks and sediments store water in pore spaces
(d) None of these
Answer:
(c) Underground layers of rocks and sediments store water in pore spaces

(iii) Give role of recharge pits.
(a) Ground water infiltration
(b) Ground water extraction
(c) Ensure ground water supply
(d) Ground water replenish
Answer:
(d) Ground water replenish

(iv) The water is extracted by:
(a) digging wells
(b) drilling pores in aquifers
(c) both (a) – (b)
(d) None of these
Answer:
(c) both (a) – (b)

Heat Transfer in Nature Extra Questions for Practice

Multiple Choice Questions (MCQs)

Question 1.
Heat transfer from the hotter part of an object to the colder part is called:
(a) conduction
(b) radiation
(c) convection
(d) all of these

Question 2.
Poor conductors of heat are:
(a) clay
(b) porcelain
(c) both (a) – (b)
(d) all of these

Question 3.
In Mori back of Uttarkanshi homes are made of:
(a) Two wooden layer walls
(b) Three wooden layer walls
(c) Four wooden layer walls
(d) None of these

Question 4.
Water, air get heated by:
(a) convection
(b) radiation
(c) conduction
(d) none of these

Question 5.
The movement of cooler air from sea to land is known as:
(a) sea breeze
(b) land breeze
(c) none of these
(d) all of the above

Question 6.
Heat transfer directly occurs from fire to us. It is called ______.
(a) convection
(b) radiation
(c) none of these
(d) all of these

Very Short Answer Type Questions:

Question 1.
Name fastest method of heat transfer.

Question 2.
A mettalic bridges expands in summer. What precautions are taken to make sure this expansion of metal does not cause damage to the bridge?

Question 3.
Compare a conductor to an insulator.

Question 4.
Water in lakes, rivers, sea evaporates as water vapours. Why?

Short Answer Type Questions:

Question 1.
Write two poor conductors of heat.

Question 2.
What are (a) sea breeze, (b) land breeze?

Question 3.
How is ground water depleted?

Question 4.
What is rain water harvesting?

Question 5.
State and explain any two ways of heat transfer in objects.

Question 6.
How heat from fire reaches us ?

Question 7.
What does smoke consist of?

Question 8.
Why are metal utensils used for cooking ?

Long Answer Type Questions:

Question 1.
Perform an activity to show conduction of heat. Draw a figure.

Question 2.
List some materials around you which are insulators and why?

Question 3.
List the uses of radiation in our day-to-day life.

Question 4.
Show seepage of water beneath the earth by an experiment. Also draw a figure to compare flow of water via sand, gravel and clay.

Question 5.
How are ground water resources recharged? Discuss briefly.

Students can use Class 7 Science Curiosity Extra Questions and Chapter 6 Adolescence A Stage of Growth and Change Extra Question Answer to prepare effectively at home.

Class 7 Science Chapter 6 Adolescence A Stage of Growth and Change Extra Questions

Class 7 Science Chapter 6 Extra Questions on Adolescence A Stage of Growth and Change

Adolescence A Stage of Growth and Change Class 7 Very Short Question Answer

Question 1.
Name the stage of growth and change in humans.
Answer:
Adolescence.

Question 2.
Write any two observable changes during growing up.
Answer:
Increase in height, weight gain.

Question 3.
Do boys develop a moustache and beard?
Answer:
Yes.

Question 4.
Define menstruation.
Answer:
Blood is discharged from the body of a female in this cyclic phase every month in it.

Question 5.
When does menstruation naturally stop in females?
Answer:
At the age of 45-55 years in women.

Question 6.
Name an emotional change in adolescents.
Answer:
Mood swings or strong emotions.

Question 7.
Name a food source that helps to optimal bone growth.
Answer:
Milk.

Question 8.
Give the role of MHS about menstrual hygiene.
Answer:
It distributes sanitary pads free to females or adolescent girls in India’s rural areas at reduced rates.

Question 9.
Which platform is used for the collective well-being of people?
Answer:
Online platform, social media, etc.

Question 10.
Write one remedy for substance abuse.
Answer:
Say “No” to substance abuse. Avoid it to remain healthy.

Question 11.
What is the term used for chemical secretions responsible for changes taking place in the body?
Answer:
Hormones

Question 12.
Name one emotional change seen during adolescence.
Answer:
Mood swings

Question 13.
What physical changes occur in girls during puberty?
Answer:
Breast development and the onset of the menstrual cycle.

Question 14.
Name the disease caused by less or no secretion of thyroxine hormone by the thyroid.
Answer:
Goitre

Adolescence A Stage of Growth and Change Class 7 Short Question Answer

Question 1.
What do you mean by personal hygiene?
Answer:
Personal hygiene means keeping our body clean by bathing daily, washing hands, brushing teeth, and wearing clean clothes.

Question 2.
State use of social media.(M.Imp.)
Answer:
Social media are now-a-days available due to modern technology. You can talk on it, or send an information on it. You may interact or also share an information to each other. Seek help and guidance of elders, teachers and parents to use this platform. It will surely help you since this is responsible for collective well-being of all of us.

Question 3.
What is puberty? Discuss in brief.(Imp.)
Answer:
This refers “to a stage of life when our body becomes capable of reproduction”. In boys, normally, it is 11-16 years but in girls it is 10-15 years. It can vary from person to other person at all.

Question 4.
Write note on (a) Adolescence (b) Adolescent.
Answer:
(a) Adolescence: This is defined “as a period of transition from a child to an adult”.
(b) Adolescent: A child reaches puberty, then he or she becomes an adolescent at all.

Question 5.
Write changes at puberty.
Answer:
Testis/ovaries start releasing hormones. Secondary sex characteristics are visible at this stage like development of mammary glands in females. Change in behaviour and attitude is most observable. It is a natural part of growing up. These seems no reason to feel insecure. Moreover, sexual feelings develop.

Question 6.
Explain in brief “menstrual cycle”.
Answer:
It refers “to cyclic changes once in a month lasting upto 1-4 days time followed by bleeding in girls/females releasing an egg”. In human females, it a cycle of reproducing as well as releasing one mature egg, uterus wall thickening its shedding, if fertilization does not take place is known as the menstrual cycle. It is controlled by hormones. It stop at age of 45-55 years, it is called menopause at all.

Question 7.
What is the function of iron? Name some iron- rich food items.
Answer:
Iron helps in the formation of haemoglobin in the blood, which carries oxygen to all parts of the body. Green leafy vegetables, jaggery, meat and citrus fruits are rich in iron.

Question 8.
“The age of adolescence is joyful”. How?
Answer:
Good habits, thoughtful decisions as well as tiny actions have positive effect on adolescents. The excitement along with curiosity give a new view point about all things near them. This journey is unparallel in it self also.

Question 9.
What do understand by the term adolescence?
Answer:
Adolescence is the stage of development between childhood and adulthood which starts at the age of 10 years and continue upto 19 years of age.

Question 10.
What do you understand about a balanced diet?
Answer:
The food containing proteins, carbohydrates, fats and vitamins in requisite proportions is called a balanced diet.

Question 11.
What is menstruation?
Answer:
The phase of the menstrual cycle when blood discharge occurs from the female body is referred to as menstruation.

Question 12.
How can we keep our bodies healthy?
Answer:
We can keep our bodies healthy by doing regular physical activities, eating nutritious food, and maintaining good personal hygiene.

Question 13.
Write two physical activities important during adolescence.
Answer:
Two important physical activities during adolescence are moderate to vigorous intensity aerobic activities and muscle-strengthening activities. These activities help adolescents maintain a healthy weight, build strong bones and muscles, and improve overall fitness during this crucial stage of development.

Question 14.
Write a note on “cyberbulling”.(V.Imp.)
Answer:
This includes use of digital devices. Computers, phones and the online plateforms are used in it. It is done to harass other people sending them false, misleading messages. If some one sends you false message or rumours, you can locate it wisely. You can take help of your parents. Always be cautions, when you upload an information or picture online. Avoid sharing of personal information to unknown or strangers etc.

Question 15.
To support menstrual hygiene, our government has introduced several initiatives. Write some of these schemes.
Answer:
MHS, RKSK, Suvidha Sanitary Napkin Initiative and some state level initiatives are introduced by our government. Some state governments have their own programmes. In Karanataka Shuchi Scheme in Tamil Nadu free sanitary napkin scheme aim to distribute free napkin to girls and females in government schools. Under MHS sanitary pads are distributed free and no charge is taken from adolescent girls in some rural zones.

Question 16.
On social media, what should be followed and what not? Make a list of these.(Imp.)
Answer:

Do’s	Don’t
1. You think before posting a remark online.	1. Do not post false information. Do not send rumours or misleading messages.
2. Always be kind and respectful to everybody.	2. Do not share your personal photos online with unknown or strangers etc.

Question 17.
Name some addictive substances and their ill effects on adolescents.
Answer:

Addictive Substances	Their ill effects on adolescents
1. Tobacco	1. Bidi, cigarettes smoking cause lung cancer. Make lungs weak.
2. Alcohol	2. Mood changes, harmful to physical and the mental health.
3. Some harmful drugs	3. Cause strong surge to take them again and again. The result is substance abuse.

Question 18.
Write notes on:
(a) Adam’s apple
(b) Secondary sexual characters
Answer:
(a) Adam’s apple: The protruding part of the throat in boys is called Adam’s apple. It is the enlarged voice box. It makes the voice of boys hoarse.
(b) Secondary sexual characters: The characters which help to distinguish males from females are called secondary sexual characters. These characteristics can be hair on the chest, face and underarms; the development of breasts in girls, beards and moustaches in boys.

Question 19.
Enlist certain myths about menstruation.
Answer:
Physical isolation of menstruating girls is still prevalent in our society. It is a natural process. The myths has no scientific reason or basis. Encourage scientific outlook towards menstruation. We should help girls towards good reproductive health of women. We should contributively to healthy life style of women or girls in our society.

Question 20.
Lila always eats only dal and rice in every meal. She often falls ill and has become prone to diseases. Can you suggest changes in her diet which can make her healthy and free from disease?
Answer:
A balanced diet includes adequate amount of proteins, carbohydrates, fats and vitamins to stay healthy. Lila’s diet is not a balanced diet as she takes only proteins and carbohydrates in every meal. She should include vitamins, and minerals in her meal to protect her from various diseases. She should take milk, fruits, nuts, cereals, pulses, and iron rich diet including leafy vegetables, jaggery, meat, and citrus fruits.

Question 21.
Mention any two features that are seen in boys and girls each to distinguish them from each other at puberty.
Answer:
Two features seen in boys at puberty are:
Growth of facial hairs
Voice becomes hoarse.

Two features seen in girls at puberty are:
Development of breasts.
The region below the waist becomes wider.

Question 22.
We should avoid taking medicines/drugs unless prescribed by a doctor. Give reasons.
Answer:
We should avoid taking medicines/drugs unless prescribed by a doctor because taking the wrong medicine can harm our body and cause side effects. Misusing drugs can lead to drug addiction, which can seriously affect our health.

Question 23.
Name three changes experienced from adolescence to adulthood and one example of the challenges associated with each of them?
Answer:
Three changes experienced form adolescence to adulthood include physical, intellectual, psychological and social challenges. The changes are rapid and often take place at different rates.
Example for physical – body odor, acne, and more body hair
Example for psychological – During adolescence, your child will begin to observe, measure and manage their emotions
Example for social challenges: Adolescents spend less time with their families and may focus more on their peers however adults spend more time with themselves or family

Question 24.
Which changes indicate reproductive capability in girls? Explain
Answer:
In adolescent girls, the menstrual cycle is the primary indicator of reproductive capability. This cycle, along with other physical changes like breast development and the start of pubic hair growth, signifies the body’s readiness for reproduction. The menstrual cycle is a series of natural changes that occur in a woman’s body to prepare for a possible pregnancy. It involves the monthly release of an egg (ovulation) and the thickening of the uterine lining. If the egg is not fertilized, this lining is shed, resulting in menstruation. The menstrual cycle is a sign of good reproductive health and the body’s ability to conceive and carry a pregnancy. While the menstrual cycle is the most prominent, other physical changes during adolescence in girls, such as breast development, growth of pubic hair, and widening of hips, also indicate the onset of reproductive maturity.

Adolescence A Stage of Growth and Change Class 7 Long Question Answer

Question 1
Explain personal hygiene of adolescents. (Imp.)
Answer:
For personal hygiene, nutrition is necessary for growing up into adult. Maintain hygiene of armpits, pubic region specially. This protects us from potential infection. In girls, proper hygiene is necessary during menstruation. So girls should use sanitary pads made of reusable cloth. Government sells these at low price to girls and women. Reduce stigma about sanitary pads and dispose off then safely. Now-a-days biodegradable sanitary pads are available. They are environment friendly too for us all in society.

Question 2.
Rahul and his classmates eat potato chips and burgers regularly after having their lunch during recess at school. Are these are healthy eating habits? Give reasons.
Answer:
No, eating potato chips and burgers regularly is not a healthy habit as they are high in fat, sugar, and salt, but they lack the necessary nutrients needed for the body to stay healthy. Adolescents requires the consumption of a balanced diet containing an adequate proportion of nutrients like proteins, carbohydrates, fats, vitamins and minerals to stay healthy. Therefore, an adolescent person should take an adequate amount of nutrients in his/her diet.

Question 3.
Explain the importance of emotional changes during adolescence.
Answer:
During adolescence, hormonal changes not only affect the body but also influence emotions. Adolescents may experience mood swings, confusion, anxiety, or a desire for independence. These emotional changes are natural but can be overwhelming. Importance of emotional changes:

• They help in developing self-identity.
• They prepare individuals for adult responsibilities.
• They contribute to the development of reasoning and decision-making.

Question 4.
What are harmful substances ? How can we avoid them ?
Answer:
Harmful substances are life threating drugs, bidis, tobacco, cigarettes, alcohol etc. Some people create peer pressure or force you to consume them. Due to excitement, youngs are attempted to these. They get influenced by some people and take them to enjoy.
The substances affect our physical and mental state body. They, it taken regularly cause addiction. So to avoid them say “No”. Leave them and do not use at any cost. Leave surge about them to remain in healthy.

Question 5.
Describe the role of hormones during adolescence.
Answer:
Hormones are chemicals which play significant roles in growth, development of body. For proper functioning of body they are needed at all. Hormones are chemicals produced by our body in various parts.
Hormones are released at proper time in response to signals from our brain. Hormones also affect our behaviour and mood changes in adolescents due to hormones are visible.

Question 6.
Make a list of secondary sexual characteristics in boys and girls.
Answer:
Secondary Sexual Characteristics in Boys:

• Growth of facial and body hair: This includes beards, mustaches, and hair on the chest, arms, legs, and pubic area.
• Deepening of the voice: The voice box (larynx) enlarges, causing the voice to become lower and huskier.
• Broadening of the shoulders: The shoulder girdle (shoulders and upper back) widens due to muscle development.
• Increased muscle mass: Muscles grow, especially in the upper body, making boys appear more muscular.
• Enlargement of the Adam’s apple: The Adam’s apple (laryngeal prominence) becomes more prominent in the throat.
• Growth of the penis and testes: These are primary sexual characteristics, but they also develop further during puberty, and the testes begin producing sperm.

Secondary Sexual Characteristics in Girls:

• Breast development: Breasts enlarge and develop due to hormonal changes.
• Widening of the hips: The hip bones widen, giving the body a more rounded shape.
• Onset of the menstrual cycle: The body begins to prepare for potential pregnancy, with the shedding of the uterine lining (menstruation).
• Growth of pubic and underarm hair: Hair develops in the pubic area and underarms.
• Increased body fat: Fat distribution changes, with more fat accumulating around the hips and thighs.
• Development of a higher-pitched voice: While less pronounced than the deepening of the voice in boys, a slight. increase in pitch can occur.

Adolescence A Stage of Growth and Change Class 7 Case Based Questions

1. Read the following passage carefully and answer the questions that follow:
The adolescents show several physical and internal changes in their body to grow and reach adulthood. The changes may be increase in height, weight gain, body appearance, strength etc. Some changes in voice, growth of facial as well as chest hair in the boys and breat development in girls distinguishes a male from a female. Hence, these characteristics are known as secondary sexual characteristics. These natural signs mark onset of puberty in males and females. They also exhibit that the body of a girl and a boy is preparing for adulthood and some indicative of reproduction.

(i) What is adolescence?
(a) A developmental stage between childhood and adulthood.
(b) It is a stage between 10 to 18 years of age.
(c) None of these
(d) All of these
Answer:
(a) A developmental stage between childhood and adulthood.

(ii) Some observable changes in voice, hair, and breasts help us to recognise a male from a female. They are:
(a) change in voice
(b) growth facial, chest hairs in boys
(c) development of breats in a girl
(d) all of these
Answer:
(d) all of these

(iii) Some changes during adolescence are ;
(a) easily observable
(b) not involved in reproduction directly
(c) help to distinguish a male from a female
(d) all of these
Answer:
(d) all of these

2. Read the following passage carefully and answer the questions that follow:
Venkatesh noticed that during the last year, his voice deepened, he gained height, and started developing a faint moustache. His cousin Devyani also experienced visible changes-her height increased, and her skin developed acne. Their teacher explained that these are normal signs of adolescence, a stage between 10 to 19 years marked by physical, emotional, and mental development. She emphasized that these changes occur at different times and in varying degrees in each individual due to hormonal activity and genetic factors.

(i) Which of the following is a secondary sexual characteristic in boys?
(a) Development of reproductive organs
(b) Broadening of shoulders
(c) Formation of sperm
(d) Increase in height
Answer:
(b) Broadening of shoulders

(ii) Which organ in the throat enlarges during adolescence and leads to voice change in boys?
(a) Thyroid gland
(b) Tonsils
(c) Voice box
(d) Pituitary gland
Answer:
(c) Voice box

(iii) Acne or pimples during adolescence are mainly caused by:
(a) Poor nutrition
(b) Increased sweat
(c) Bacterial infections only
(d) Oily secretions blocking skin pores
Answer:
(d) Oily secretions blocking skin pores

(iv)Which emotional change is commonly experienced during adolescence?
(a) Baldness
(b) High blood pressure
(c) Mood swings
(d) Frequent sleepwalking
Answer:
(c) Mood swings

Adolescence A Stage of Growth and Change Class 7 Picture Based Questions

1. Observe the image given below and answer the following questions:

(i) What is the bump on boy’s throat called?
(a) Adam’s Apple
(b) Adam’s Eye
(c) Adam’s throat
(d) Adam’s voice
Answer:
(a) Adam’s Apple

(ii) Is this change noticeable in all boys?
(a) No
(b) Yes
(c) 50-50
(d) Both (b) and (c)
Answer:
(a) No

(iii) Why is there change in the adolescence boys’ voice?
Answer:
In adolescent boys the growth of the voice box leads to a voice that sounds hoarse. This change to change in voice.

2. Observe the image given below and answer the following questions:

(i) Name the digital devices used in cyberbullying?
(a) Computers
(b) Phones
(c) Onlie platforms
(d) All of these
Answer:
(d) All of these

(ii) Cyberbullying, one should be cautious:
(a) while uploading pictures
(b) sharing information with strangers
(c) teasing
(d) both (a) and (b)
Ans wer:
(d) both (a) and (b)

(iii) If anyone bully you, what should you do individually?
Answer:
If someone tries to bully you, it is important not to feel scared or helpless. Rather, handle it wisely and seek help from parents and teachers.

Adolescence A Stage of Growth and Change Extra Questions for Practice

Multiple Choice Questions (MCQs):

Question 1.
Menstruation and signs of puberty are due to:
(a) Hormones
(a) and (b)
(b) Certain chemicals
(c) Both
(d) None of these

Question 2.
Addictive substances are:
(a) tobacco
(b) bidis
(c) cigarettes
(d) all of these

Question 3.
To overcome addiction:
(a) seek help from family
(b) seek help from friends
(c) talk to your teachers
(d) all of these

Question 4.
Some serious health problems caused due to consumption of harmful substances are:
(a) memory loss
(b) breathing problems
(c) damage to the lungs
(d) all of these

Question 5.
Cyberbullying involves:
(a)use of phones, computers, online platforms to harass someone
(b) sending wrong messages
(c) both (a) and (b)
(d) None of these

Very Short Answer Type Questions:

Question 1.
What do you call stage of growth and change?

Question 2.
Write one most observable change in adolescents.

Question 3.
What is voice box?

Question 4.
Why is a nutritions diet necessary for the adolescents?

Question 5.
How do emotions influence our life?

Short Answer Type Questions:

Question 1.
Why is it necessary to avoid substance abuse?

Question 2.
Name two changes that are faced by adolescents.

Question 3.
Give the functions of: (a) RKSK (b) MHS

Question 4.
What are positive impacts of good habits and good actions on adolescents?

Question 5.
What are natural sign in an adolescent body that show that our body is preparing for adulthood?

Short Answer Type Questions:

Question 1.
Write any two common myths about menstruation.

Question 2.
What do you know about:
(a) acne
(b) pimples

Question 3.
Explore any two diverse behavioural changes in adolescents.

Question 4.
How can parents support their adolescents during this transitional phase?

Question 5.
Name some physical activities that are very necessary during adolescence period.

Long Answer Type Questions:

Question 1.
Explain any four initiatives started by our government to support the menstrual hygiene.

Question 2.
Write any four locally available foods, their sources, nutrients present in them and functions of these nutrients.

Question 3.
Write short notes on:
(a) Puberty
(b) Menstruation and
(c) Adolescence

Question 4.
How do we grow with age? What are teenage years? Write some observable changes

Students can use Class 7 Science Curiosity Extra Questions and Chapter 5 Changes Around Us Physical and Chemical Extra Question Answer to prepare effectively at home.

Class 7 Science Chapter 5 Changes Around Us Physical and Chemical Extra Questions

Class 7 Science Chapter 5 Extra Questions on Changes Around Us Physical and Chemical

Changes Around Us Physical and Chemical Class 7 Very Short Question Answer

Question 1.
Write of change is physical or chemical.
(a) Cutting of wood
(b) Beat aluminium to make foil
(c) Milk change into curd
(d) Sediment formation
Answer:
(a) Physical change
(b) Physical change
(c) Chemical change
(d) Physical change

Question 2.
Name chemical present in vinegar.
Answer:
Acetic Acid.

Question 3.
Baking soda is mixed to lemon juice, bubbles are formed with formation of a gas. Name the gas.
Answer:
Carbon dioxide.

Question 4.
What type of change is called in which new substance with new properties is formed?
Answer:
Chemical change

Question 5.
Combustion, cooking, and rusting are chemical changes, justify the statement.
Answer:
In all these processes, new substances are being formed.

Question 6.
Give two examples of a chemical change.
Answer:
(i) Rusting of iron (ii) Curdling of milk

Question 7.
What is the colour of flame when magnesium ribbon is burnt?
Answer:
White colour

Question 8.
During rusting, which new substance is formed?
Answer:
Iron oxide

Question 9.
Define ignition temperature.
Answer:
The minimum temperature of a substance at which it catches fire is called its ignition temperature.

Question 10.
When baking soda is mixed with vinegar then a gas is released. Name the gas.
Answer:
Carbon dioxide

Question 11.
What is the colour of rust?
Answer:
Reddish brown colour

Question 12.
Gives examples of natural slow changes.
Answer:
Weathering of rocks and erosion

Question 13.
Name two desirable changes.
Answer:
Formation of curd or paneer from milk, decomposition of food waste into compost.

Question 14.
When water is frozen, ice is formed. Ice has different properties. Why do we call it a physical change ?
Answer:
Because no new substance is formed.

Question 15.
Name a process where physical and chemical changes occur.
Answer:
Burning of a candle.

Changes Around Us Physical and Chemical Class 7 Short Question Answer

Question 1.
Give one example of irreversible change.
Answer:
Rusting of iron.

Question 2.
Write an example of chemical change in following:
(a) Evolution of gas
(b) Evolution of heat
Answer:
(a) Vinegar is mixed to baking soda.
(b) Magnesium is burnt in air.

Question 3.
Name any three combustible substances.
Answer:
(a) Cotton, (b) Wood, (c) Kerosene oil.

Question 4.
What are three requirements of combustion?
Answer:
(a) Heat (permit a fuel to reach ignition temperature)
(b) Oxygen and
(c) Fuel

Question 5.
The ice melts, but we can refreeze it into ice. What type of change is it?
Answer:
It is a physical change that can be reversed too.

Question 6.
Name two changes in rocks to make soil.
Answer:
(a) Physical change and
(b) Chemical change

Question 7.
Give the chemical reaction for the burning of magnesium.
Answer:
Magnesium + Oxygen ⟶ Magnesium Oxide + Light + Heat↑

Question 8.
Why does lime water turn milky if O₂ is passed through it?
Answer:
Lime water + CO₂ ⟶ It turns milky.
Lime water + Carbon dioxide ⟶ Calcium Carboneate + Water

Question 9.
What are physical properties?
Answer:
The properties such as shape, size, colour, and state of a substance that can be observed are called physical properties.

Question 10.
What are physical changes?
Answer:
The changes in which a substance undergoes a change in its physical properties are called physical changes.
Physical changes are generally reversible. In such changes, no new substances are formed. For example, melting of ice, formation of steam, etc.

Question 11.
What is chemical change?
Answer:
A change in which one or more new substances are formed is called a chemical change. A chemical change is caused by a chemical reaction. For example, formation of curd from milk, burning of paper, etc.

Question 12.
Define rusting. How can it be prevented?
Answer:
Rust formation on iron is called Rusting. It can be prevented by oiling, painting, greasing etc.

Question 13.
Some changes observed around us are as follows:
Burning of wood, Boiling of water, Freezing of water, burning of a candle, water added to beetroot extract.
Select Reverse and Irreversible changes.
Answer:

Reversible changes	Irreversible changes
1. Boiling of water	1. Burning of wood
2. Freezing of water	2. Burning of candle

Question 14.
Explain how water can exist in solid, liquid, and gas forms.
Answer:
Water exists in three states. When heated, water becomes gas; when frozen, water becomes ice (solid); ice melts to liquid water.

Question 15.
Distinguish between a physical and a chemical change.
Answer:
Difference between physical and chemical changes:

A Physical change	A Chemical change
1. Only change in appearance. No new substances is formed.	1. New substance formed.
2. e.g., chalk converted into powder.	2. e.g., candle burns to make vapours and wax.
3. Reversible change	3. Reversible change.

Question 16.
What is combustion? Name any combustible substance. What are three requirements of combustion?
Answer:
(a) Combustion is “a chemical reaction in which a substance reacts to oxygen and heat is produced along with a new substance.”
(b) Kerosene is a combustible substance.
(c) It needs fuel, oxygen, and heat.

Question 17.
What do you know about a scientist named Michael Faraday?
Answer:
He delivered a series of lectures. He stated that a candle was perfect object for scientific studies. He made some important contributions in various fields of science. He discussed physical as well as chemical processes. Various processes such as combustion and melting was discussed by him in the nineteenth century at all.

Question 18.
How would you explain candle burning in terms of physical and chemical changes?
Answer:
A candle burns. The wax melts. Vapours are formed. Wax vapours produce a flame. This includes solidification and evaporation. Both are physical changes. Burning of the vapours is chemical change. We can conclude that candle burning is a physical and a chemical change at all.

Question 19.
Enlist five chemical changes. (V. Imp.)
Answer:
(a) Rusting of iron, (b) formation of a new substance when magnesium is burnt in air, (c) burning of a candle, (d) water is added in beetroot extract and (e) burning of magnesium.

Question 20.
What does burning of a candle show?
Answer:
(a) Wax of candle melts, (b) is carried up the wick, (c) and evaporates due to heat, (d) vapour of wax burns and produces flame.
All of these are physical changes at all. On the contrary, the burning a vapour is a chemical change.
Conclusion: Both physical and chemical changes occur during burning of a candle.

Question 21.
A substance may change in appearance but not remain same. Justity. (V. Imp.)
Answer:
Blow air into water. It creates bubbles only. There is no change in water. When you blow air in the lime water; it creates bubbles. The air changes colour as it becomes milky or even cloudy. After some time, a white substance is formed. It shows that a new substance is formed. It is a chemical change.

Question 22.
Analyse the chemical equation given below:
Lime water + Carbon dioxide → Calcium Carbonate + Water.
Answer:
Carbon dioxide reacts will lime water and forms a new substance named calcium hydroxide. But it is not soluble in water. It is a chemical change formed by a chemical reaction at all. Calcium Carbonate is insoluble in water.

Changes Around Us Physical and Chemical Class 7 Long Question Answer

Question 1.
Are all changes permanent? Explain by citing example. (M. Imp.)
Answer:
When a thing undergoes change, it can return to an original form. It means changes can be reversed e.g., the ice melts; and it can be frozen into ice also. Another example is that water evaporates; may be condensed back into liquid water also. But certain changes cannot be reversed like chopped vegetables do not come to its original shape and size. Other example is of popcorn – making it cannot go back to its shape at all.
So there are two types of change (a) one that is reversed, (b) another cannot be reversed i.e., irreversible.

Question 2.
Explain weathering of rocks. (M. Imp.)
Answer:
Weathering is the process by which rocks are broken down into smaller pieces, eventually forming soil. It occurs through both physical and chemical changes. Physical weathering occurs when large rocks break into smaller pieces without changing their chemical composition. This can be caused by change in temperature due to climate, the growth of tree roots, or the freezing of water within cracks in the rocks. Chemical weathering happens when water or chemicals in the water react with the minerals in rocks, changing their composition. For example, a black coloured rock called basalt, which contains iron, undergoes a chemical change. When exposed to water or moist air for a long time, the iron reacts with oxygen to form iron oxide, which gives the rock a red colour.

Question 3.
How would you prove that oxygen is necessary for combustion? (V. Imp.)
Answer:
Aim: Lets find out whether the presence of oxygen is essential for combustion.

Material Required: One glass tumbler, two identical candles, two petridishes etc.

Procedure:

1. Place two candles on two separate petridishes, light them with matchbox.
2. Cover one of the candles with a glass tumbler.
3. Record your observations.

Observations:

1. The candle that was not covered as in Fig. (a) continues to burn.
2. The covered candle as in Fig. (b) stops burning after some time.

Inference
Oxygen from the air is essential for combustion. If you cover a burning candle, it cannot get air and the flame goes out because there is no oxygen to support burning. You can test the carbon dioxide gas by adding a small amount of lime water in the petridish. You will notice that it turns milky due to the formation of calcium carbonate. This confirms that oxygen is required for combustion.

Changes Around Us Physical and Chemical Class 7 Case Based Questions

1. Read the following passage carefully and answer the questions that follow:
The sediments lie at the base of mountains. They are formed by physical changes. These changes break big rocks into smaller ones. Several causes of it are climatic, temperature conditions, water freezing in cracks of the rocks as well as roots of plants which are growing there. All these cause breaking of the rocks. Chemical present in water react to rocks and change their composition also. This is called a physical change.

(i) How are physical changes in rocks caused?
(a) Temperature changes
(b) Tree roots are growing in rocks
(c) The freezing water found there
(d) All of these
Answer:
(d) All of these

(ii) How are rocks formed?
(a) Sediments lie at base of mountains
(b) Physical change take place in them
(c) Both (a) and (b)
(d) None of these
Answer:
(c) Both (a) and (b)

(iii) Does any chemical change occur there?
(a) Chemical in water react to rocks
(b) Changed rock composition
(c) Its cause is water or chemicals in it
(d) All of these
Answer:
(d) All of these

(iv) How are rocks formed?
Answer:
Rocks are formed by physical and chemical changes in sediments. The big rocks break into smaller ones. Some factors affect this as temperature, chemicals of water etc.

2. Read the following passage carefully and answer the questions that follow:
The Case of the Melting Ice and Inflated Balloons
During a group discussion, students shared everyday changes they had observed-ice cubes melting, paper being folded, and balloons inflating or bursting. Their teacher explained that these are all examples of physical changes, which may alter the size, shape, or state of matter, but do not produce new substances. They also discussed reversible and irreversible changes.

(i) When ice melts into water, what type of change occurs?
(a) Physical and reversible
(b) Physical and irreversible
(c) Chemical and reversible
(d) Chemical and irreversible
Answer:
(a) Physical and reversible

(ii) Bursting of an inflated balloon is:
(a) A reversible physical change
(b) An irreversible physical change
(c) A chemical change
(d) None of these
Answer:
(b) An irreversible physical change

(iii) Folding paper into different shapes (like origami) is classified as:
(a) Physical and irreversible
(b) Chemical and irreversible
(c) Physical and reversible
(d) Chemical and reversible
Answer:
(c) Physical and reversible

(iv) What is a common feature of all physical changes?
(a) Formation of a new substance
(b) Permanent colour change
(c) Only physical properties like shape or state change
(d) Emission of light
Answer:
(c) Only physical properties like shape or state change

Changes Around Us Physical and Chemical Class 7 Picture Based Questions

1. Look at the picture and answer the following questions:

(i) What does the above given Fig. (a) show?
(a) Focusing sunrays using a magnifying glass
(b) Focusing light to ignite paper
(c) Light passing through a magnifying glass
(d) None of these
Answer:
(a) Focusing sunrays using a magnifying glass

(ii) What does Fig. (b) show?
(a) Making a hole through paper
(b) Paper catches fire
(c) Sunrays heat up the paper
(d) None of these
Answer:
(b) Paper catches fire

(iii) What is called ignition temperature?
Answer:
Focusing sunrays on the paper heats it. The temperature of the paper increases with time. After some time, the paper becomes so hot that it starts burning. This minimum temperature at which a substance catches fire is called its ignition temperature.

2. Look at the picture and answer the following questions:

(i) What does this figure show?
(a) Action of an acid over sodium carbonate
(b) Action of sodium carbonate on acid
(c) Release of gas
(d) None of these
Answer:
(a) Action of an acid over sodium carbonate

(ii) Name the gas released.
(a) Oxygen
(b) Hydrogen
(c) Carbon dioxide
(d) Nitrogen
Answer:
(c) Carbon dioxide

(iii) How is lime water affected?
Answer:
The lime water becomes milky.

Changes Around Us Physical and Chemical Extra Questions for Practice

Multiple Choice Questions (MCQs)

Question 1.
Select the correct option:
(a) Vinegar + Baking soda ⟶ Carbon dioxide + Other substances
(b) Vinegar +O₂ ⟶ CO₂+ Other substances
(c) Vinegar + Iron ⟶ Carbon dioxide + Other substances
(d) None of these

Question 2.
Which one is correct?
(a) A cube of ice melts
(b) A rose plant grows to form a flower
(c) On a banana, brown spots develop after five days
(d) All of these

Question 3.
Select the physical change:
(a) A piece of paper is folded to create new objects
(b) A chark crushed to make powder
(c) Ice cubes melt
(d) All of these

Question 4.
A candle burns:
(a) It is a physical change
(b) It is a chemical change
(c) Both (a) and (b)
(d) None of these

Very Short Answer Type Questions:

Question 1.
Write two examples of reversible changes.

Question 2.
Explain the process of rust formation of iron.

Question 3.
How would you test for carbon dioxide gas formed after burning of a candle?

Question 4.
Write two combustible substances.

Short Answer Type Questions:

Question 1.
What is needed to start combustion?

Question 2.
What changes occur when a candle is lit?

Question 3.
Write the events when a candle burns.

Question 4.
Mention two changes that can be reversed and two changes that cannot be reversed.

Question 5.
Write about the weathering of rocks.

Question 6.
How is soil formed?

Question 7.
In a nutshell, briefly explain erosion.

Question 8.
Some changes are desirable while some are not. Explain with examples.

Long Answer Type Questions:

Question 1.
Is air is essential for combustion? Explain with the help of an activity.

Question 2.
Explain weathering of rocks.

Question 3.
Which gas is released when vinegar and baking soda are mixed? What happens when this gas is passed through lime water?

Start practicing the Class 8 Ganita Prakash Solutions and Part 2 Chapter 6 Algebra Play Class 8 Question Answer to consolidate your knowledge effectively.

Class 8 Maths Ganita Prakash Part 2 Chapter 6 Solutions

Class 8 Maths Algebra Play Solutions

Class 8 Ganita Prakash Part 2 Chapter 6 Solutions Algebra Play

NCERT (Page 136)

Question 1.
(i) How would you change this game to make the final answer 3? What about 5?
Solution:
We can understand such tricks through algebra.
Step 1: Think of a number = x
Step 2: Triple it = 3x
Step 3: Add 9 = 3x + 9
Step 4: Divide by 3 = \(\frac{3 x+9}{3}\) = x + 3
Step 5: Subtract the original number you thought of (x + 3) – x = 3.
For Example:
Consider a number 23.
Triple it = 3 × 23 = 69
Add 9 = 69 + 9 = 78
Divide by 3 = 78 ÷ 3 = 26
∴ 26 – 23 = 3

To make the final answer 5.
Step 1: Think of a number = x
Step 2: Double it = 2x
Step 3: Add 10; 2x + 10
Step 4: Divide by 2 = \(\frac{2 x+10}{2}\) = x + 5
Step 5: Subtract the original number = x + 5 – x = 5

(ii) Can you come up with more complicated steps that always lead to the same final value?
Solution:
Yes, many different sequences of operations can be created.

NCERT (Page 137)

Question 1.
(i) Find the dates if the final answers are the following.
(a) 1269
(b) 394
(c) 296
Solution:
(a) Let the month be Mand the day be D.
We know that 1269 = 100 M + 165 + D
⇒ 1269 – 165 = 100M +D
⇒ 1104 = 100M + D
Here, the hundreds and thousands digits represent the month (M) and the last two digits represent the day (D).
Hence, the date is the 4th of November.
(b) Do the same as part(a). Ans 29th February
(c) Do the same as part(a). Ans 31st January

(ii) You can try this trick with your friends. Ask them to choose the starting date as their birthday.
Solution:
Do yourself

Question 2.
Can you change the steps in this trick and still find the original date? Instead of subtracting 165 from the final answer, you might have to subtract some other number.
Solution:
Yes, we can change any of the multipliers or the numbers added.
Let the month be M and the day be D.
Multiply M by 2 :2M
Add 2 : 2M + 2
Multiply by 50 : 100M + 100
Add the day : 100M + D + 100
In this new version, we should subtract 100 from the final answer instead of 165 to find the date.

NCERT (Page 139)

Question 1.
Fill the following pyramids.

Solution:

Question 2.
Fill the following pyramids.

Solution:
(i) Let us fill the empty boxes with letter-numbers.

From the rules for filling up pyramids, we get the following equation.
a + 22 = 50 ⇒ a = 50 – 22 = 28 ………(i)
b + c = a ⇒ b + c = 28 ….(ii)
c + d = 22 …(iii)
4 + e = b …(iv)
e + 6 =c …….(v)
6 + f =4 …….(vi)

On adding Eqs. (iv) and (v), we get
4 + e + e + 6 = b + c
⇒ 2e + 10 =28
⇒ 2e = 28 – 10 [from Eq. (ii)]
⇒ e = \(\frac{18}{2}\) = 9

From Eq. (iv), 4 + e = b
⇒ 4 + 9 = b [∵ e = 9]
⇒ b = 13

From Eq.(ii), b + c = 28
⇒ 13 + c = 28 [∵ b = 13]
⇒ c = 28 -13 =15

From Eq. (iii), c + 4 = 22
⇒ 15 + 4 = 22 [∵ c = 15]
⇒ 4 = 22 – 15 = 7

From Eq. (vi), 6 + f = 4 ⇒ 6 + f = 7 [∵ d = 7]
⇒ f = 7 – 6 = 1
∴ Completed pyramid is

(ii) Do same as part (i).

(iii) Do same as part (i).

Figure it Out (NCERT Page 140)

Question 1.
Without building the entire pyramid, find the number in the topmost row given the bottom row in each of these cases.

Solution:
The rule for the pyramid is to add the adjacent numbers in the lower row to get the number in the box directly above them.
(i) The bottom row is 4,13, 8.
The first number in the second row is the sum of the • first two numbers in the bottom row i.e. 4 + 13 = 17. The second number in the second row is the sum of the last two numbers in the bottom row i.e. 13 + 8 = 21
The second row is 17, 21.
The topmost number is the sum of the numbers in the second row i.e. 17 + 21 = 38.
(ii) Do the same as part (i). Ans The topmost number is 32.
(iii) Do the same as part (i). Ans The topmost number is 63.

Question 2.
Write an expression for the topmost row of a pyramid with 4 rows in terms of the values in the bottom row.
Solution:
In a number pyramid, each number is the sum of the two numbers directly below it.
Let the bottom row values be A, B, C and D from left to right.
∴ The third row values are (A + B),(B + C) and (C + D).
The second row values are
(A + B) + (B + C) = (A + 2B + C) and (B + C) + (C + D) = (B + 2C + D).
The topmost (first) row value is
A + 2B + C + B + 2C + D = A + 3B + 3C + D.

Question 3.
Without building the entire pyramid, find the number in the topmost row given the bottom row in each of these cases.

Recall the Virahanka-Fibonacci number sequence 1, 2, 3, 5, where each number is the sum of the two numbers before it.
Solution:
From the previous question, the expression for the topmost row value, if the bottom row has 4 numbers, is A + 3B + 3C + D
(i) Here, A = 8, 5 = 19, C = 21 and D = 13
Therefore, the topmost number
= 8 + 3 × 19 + 3 × 21 + 13 = 8 + 57 + 63 + 13 = 141
So, the number on top is 141
(ii) Do the same as part (i). Ans 124
(iii) Do the same as part (i). Ans 56

Question 4.
If the first three Virahanka-Fibonacci numbers are written in the bottom row of a number pyramid with three rows, fill in the rest of the pyramid. What numbers appear in the grid? What is the number at the top? Are they all Virahanka-Fibonacci numbers?
Solution:
The Virahanka-Fibonacci sequence starts with 1, where each subsequent number is the sum of the two preceding ones, i.e., 1, 2, 3, 5, 8, 13,….
The first three numbers in the sequence are 1, 2, and 3. The pyramid has three rows, so the bottom row has three numbers, the middle row has two, and the top row has one.
Each number in the row above is the sum of the two numbers directly below it.
The numbers in the middle row are calculated by summing adjacent numbers in the bottom row
i. e. 1 + 2 = 3 and 2 + 3 = 5.
The middle row numbers are 3 and 5.
The number at the top is the sum of the two numbers in the middle row, i.e., 3 + 5 = 8.
So, the top number is 8. Therefore, the numbers in the grid are 1, 2, 3, 5, and 8.
All these numbers are part of the Virahanka-Fibonacci sequence.

Question 5.
What can you say about the numbers in the pyramid and the number at the top in the following cases?
(i) The first four Virahanka-Fibonacci numbers are written in the bottom row of a four-row pyramid.
Solution:
The Virahanka-Fibonacci sequence starts with 1,
where each subsequent number is the sum of the two preceding ones i.e. 1, 2, 3, 5, 8, 13,….
The numbers in the bottom row are 1,2,3 and 5.
The second row numbers are 1 + 2, 2 + 3 and 3 + 5 i.e. 3, 5 and 8.
The third row numbers are 3 + 5 and 5 + 8 i.e. 8 and 13. So, the top number is 8 + 13 i.e. 21.
Here, we observe that, every number in the pyramid is a Virahanka-Fibonacci number and the topmost number is 21, which is the 7th Virahanka-Fibonacci number.
Hence, the number at the top of the n-row pyramid with the first nth Virahanka-Fibonacci numbers at the bottom is the (2n – 1)th Virahanka-Fibonacci number.

(ii) The first 29 Virahanka-Fibonacci numbers are written in the bottom row of a 29-row pyramid.
Solution:
The top number depends on all 29 bottom numbers, combined through repeated addition.
So, the number at the top = (2n – 1)th = 2 × 29 – 1 = 58 – 1 = 57th number from Virahanka-Fibonacci sequence.

Question 6.
If the bottom row of an n-row pyramid contains the first nth Virahanka-Fibonacci numbers, what can we say about the numbers in the pyramid? What can we say about the number at the top?
Solution:
When the bottom row uses the first n Virahanka-Fibonacci numbers = (2n – 1)th
∴ The number at the top of the pyramid = (2n – 1)th Virahanka-Fibonacci number.

NCERT (Page 142)

Question 1.
Create your own calendar trick. For instance, choose a grid a different size and shape.

Solution:
Do yourself

Question 2.
In the following grids, find the values of the shapes and fill in the empty squares:

Solution:
(i) Let the value of the black square be -x and the value of the grey circle = y
Row 1: 2x + y = 27 …(i)
Row 2: 2y + x = 21 …(ii)
From Eq. (i),y = 27 – 2x …(iii)
Now, Eq. (ii), 2(27 – 2x) + x = 21 [from Eq. (iii)]
⇒ 54 – 4x + x = 21
⇒ -3x = 21 – 54
⇒ x = \(\frac{33}{3}\) = n

On putting the value of x in Eq. (iii),
we get y = 27 – 2 × 11 = 27 – 22 = 5
So, black square = 11 and grey circle = 5
Row 3: The value of O + □ + O = y + x + y
= 5 + 11 + 5
= 21

(ii) Do the same as part (i).
Ans. Row 3: 15
Row 4: 18, 15, 15, 48

Figure it Out (NCERT Page 144)

Question 1.
Fill the digits 1, 3 and 7 in □□ × □ to make the largest product possible.
Solution:
We know that the largest digit is the multiplier. The other two digits were arranged in decreasing order to form the multiplicand.
Therefore, 31 × 7 = 217

Question 2.
Fill the digits 3, 5 and 9 in to make the largest product possible.
Solution:
We know that the largest digit is the multiplier. The other two digits were arranged in decreasing order to form the multiplicand.
Therefore, 53 × 9 = 477

NCERT (Page 144-145)

Question 1.
(i) It is now Mukta’s turn to show a mathematics trick to Shubham.

If we choose other 2-digit numbers and follow the steps, will there always be no remainder?
Solution:
Yes, there will always be no remainder.

(ii) Let’s try to understand how Mukta’s trick works. Suppose, the two-digit number is ab. When it is reversed, the new number is ba.
If b> a then ba> ab. So, the difference is (10b+a) – (10a + b) = 10b – b – 10a + a = 9b-9a = 9(b-a)
The difference is divisible by 9.
Can you work out what happens if a> b?
Solution:
The 2-digit number is ab, which can be written as 10a + b.
The reversed number is ba or 10b + a.
If a>b then ab > ba.
So, the difference is
= (10a + b) -(10b + a)
= 10 a + b – 10 b – a
= 10a – a + b – 10b
= 9a – 9b
= 9 (a – b)
The difference is 9(a – b), which is a multiple of 9 and therefore divisible by 9.

Figure it Out (NCERT Page 145-147)

Question 1.
In the trick given above, what is the quotient when you divide by 9? Is there a relationship between the two numbers and the quotient?
Solution:
The quotient is the difference between the digits of the original number.
If the tens digit is larger, the quotient is a-b.
If the unit digit is larger, the quotient is b-a.

Question 2.
In the trick given above, instead of finding the difference of the two 2-digit numbers, find their sum. What will happen? For example

• We start with 31. After reversing, we get 13.
  Adding 31 and 13, we get 44.
• We start with 28. After reversing, we get 82.
  Adding 28 and 82, we get 110.
• We start with 12. After reversing, we get 21.
  Adding 12 and 21, we get 33.

Observe that all these numbers are divisible by 11.
Is this always true? Can we justify this claim using algebra?
Solution:
Yes, it is always true that the sum is divisible by 11.
Let the original 2-digit number be represented by its digits a and b.
The value of the original number can be expressed as 10a + b.
The number obtained by reversing the digits has the value 10b +a.
The sum of these two numbers is
= (10a + b) + (10b + a)
= 10a + a + b + 10b
= 11a + 11b
= 11(a + b)
Since the sum can always be expressed as 11 multiplied by the sum of its digits (a + b), thus always divisible by 11.

Question 3.
Consider any 3-digit number, say abc (100a + 10b + c). Make two other 3-digit numbers from these digits by cycling these digits around, yielding bca and cab. Now, add the three numbers. Using algebra, justify that the sum is always divisible by 37. Will it also always be divisible by 3?
[Hint: Look at some multiples of 37]
Solution:
abc = 100a + 10b + c
bca = 100b + 10c + a
cab = 100c + 10a + b
Sum of abc + bca + cab = 111a + 111b + 111c
= 111(a + b + c)
= 37 × 3(a + b + c), is always divisible by 37.
111 = 1 + 1 + 1 = 3, is always divisible by 3.
For example:
Consider a number 153.
Other two numbers = 531 and 315
Sum = 153 + 531 + 315 = 999
999 = 37 × 27, which is divisible by 37.
999 = 9 + 9 + 9 = 27, which is also divisible by 3.

Question 4.
Consider any 3-digit number, say abc. Make it a 6-digit number by repeating the digits, that is, abcabc. Divide this number by 7, then by 11, and finally by 13. What do you get? Try this with other numbers. Figure out why it works.
[Hint: Multiply 7, 11, and 13]
Solution:
We know that a 3-digit number abc can be written as 100a + 10b + c.
So, the 6-digit number abcabc can be written as
abcabc = 100000a + 10000b + 1000c + 100a + 10b + c
= 100100a + 10010b + 1001c
= 1001(100a + 10b + c)
⇒ abcabc = 100abc
Since, 1001 = 7 × 11 × 13
When divided sequentially by 7,13 and 13, the result is always the original 3-digit number.

Question 5.
There are 3 shrines, each with a magical pond in the front. If anyone dips flowers into these magical ponds, the number of flowers doubles. A person has some flowers. He dips them all in the first pond and then places some flowers in shrine 1. Next, he dips the remaining flowers in the second pond and places some flowers in shrine 2. Finally, he dips the remaining flowers in the third pond and then places them all in shrine 3. If he placed an equal number of flowers in each shrine, how many flowers did he start with? How many flowers did he place in each shrine?
Solution:
Let x be the initial number of flowers and y be the equal number of flowers placed in each shrine.
After the first dip, the number of flowers becomes 2x.
After placing y flowers in shrine 1, the remaining flowers are 2x – y.
The remaining flowers are dipped in the second pond, so the number doubles i.e. 2(2x – y) = 4x – 2y.

After placing y flowers in shrine 2, the remaining flowers = 4x – 2y – y = 4x – 3y
The remaining flowers are dipped in the third pond.
So, the number is doubled
i. e. 2(4x – 3y) = 8x – 6y.
They are all placed in shrine 3, so this quantity must equal 3y.
8x – 6y = y
⇒ 8x = 7y
⇒ \(\frac{x}{y}=\frac{7}{8}\)
∴ The smallest positive integer solution is x = 7 and y = 8. Hence, the person started with 7 flowers and placed 8 flowers in each shrine.

Question 6.
A farm has some horses and hens. The total number of heads of these animals is 55 and the total number of legs is 150. How many horses and how many hens are on the farm?
Can you solve this without letter-numbers?
[Hint If all the 55 animals were hens then how many legs would there be? Using the difference between this number and 150 can you find the number of horses?]
Solution:
Given, the total number of heads of animals = 55
If all 55 animals were hens, each having 2 legs.
∴ The total number of legs = 55 × 2 = 110
If the total number of legs =150
∴ Remaining legs = 150 – 110 = 40
Each horse has 4 legs, which is 2 more than a hen.
This difference of 40 legs is due to the horses.
The number of horse = \(\frac{40}{2}\) = 20
So, the number of hens = 55 – 20 = 35
Hence, there are 20 horses and 35 hens on the farm.

Question 7.
A mother is 5 times her daughter’s age. In 6 yr’s time, the mother will be 3 times her daughter’s age. How old is the daughter now?
Solution:
Let d be the daughter’s current age and m be the mother’s current age.
If a mother is 5 times her daughter’s age.
∴ m = 5d . …(i)
and after 6 years, the mother will be 3 times her daughter’s age.
∴ m + 6 = 3(d + 6)
⇒ m + 6 = 3d + 18
⇒ 5d – 3d = 18 – 6 [From Eq. (i)]
⇒ 2d = 12
⇒ d = \(\frac{12}{2}\) = 6
From Eq. (i), we get
m = 5 × 6 = 30
Hence, the daughter is currently 6 yr old.

Question 8.
Two friends, Gauri and Naina, are cowherds. One day, they pass each other on the road with their cows. Gauri says to Naina, “You have twice as many cows as I do”. Naina says, “That’s true, but if I gave you three of my cows, we would each have the same number of cows”. How many cows do Gauri and Naina have?
Solution:
Let x and y be the number of cows of Gauri and Naina.
According to the question,
2x = y …(i)
Also, x + 3 = y – 3
x – y = -3 – 3 = -6 ……(ii)
From equations (i) and (ii), we get
x – 2x = -6
⇒ -x = -6
⇒ x = 6
Putting x = 6 in equation (i), we get,
y = 2 × 6 = 12
Thus, Gauri and Naina have 6 and 12 cows, respectively.

Question 9.
I run a small dosa cart, and my expenses are as follows.

• Rent for the dosa cart is ₹ 5000 per day.
• The cost of making one dosa (including all the ingredients and fuel) is ₹ 10.

(i) If I can sell 100 dosas a day, what should be the selling price of my dosa to make a profit of ₹ 2000?
(ii) If my customers are willing to pay only ₹ 50 for a dosa, how many dosas should i aim to sell in a day to make a profit of ₹ 2000?
Solution:
Given, rent for the dosa cart = ₹ 5000 per day and the cost of one dosa= ₹ 10
(i) The total expenses for making 100 dosas
= Fixed rent + Cost per dosa × Number of dosa = 5000 + 10 × 100
= 5000 + 1000
= 6000

To make a profit of ₹ 2000, the total revenue needed is
= Total expenses + Desired profit
= 6000 + 2000
= 8000
So, selling price per dosa = \(=\frac{\text { Total revenue needed }}{\text { Number of dosas sold }}\)
Hence, the selling price of the dosa should be ₹ 80 to make a profit of ₹ 2000.

(ii) Let M = Number of dosas to sell
∴ Revenue = 50M
and total cost = 5000 + 10 × n = 5000 + 10M
We know that
Revenue – Cost = Profit
⇒ 50M – (5000 + 10 n) = 2000
⇒ 50n – 5000 – 10n = 2000
⇒ 40M = 7000
⇒ M = 175
Hence, need to sell 175 dosas in a day to reach the profit goal at the given price.

Question 10.
Evaluate the following sequence of fractions.
\(\frac{1}{3}, \frac{(1+3)}{(5+7)}, \frac{(1+3+5)}{(7+9+11)}\)
What do you observe? Can you explain why this happens?
[Hint: Recall what you know about the sum of the first n odd numbers]
Solution:
Here, the first three fractions in the sequence are \(\frac{1}{3}, \frac{1+3}{5+7}\)
and \(\frac{1+3+5}{7+9+11}\) i.e. \(\frac{1}{3}, \frac{4}{12}\) and \(\frac{9}{27}\)
So, the value of each fraction in the sequence is consistent.
Since the sum of the first n odd numbers = n²
Here, the numerators are sums of the first n odd numbers.
The denominator is the sum of the next n odd numbers after the first n.
The first 2M odd numbers sum to (2M)².
The sum of the first n odd numbers is n².
Therefore, the sum of the next n odd numbers (the denominator) = (2M)² – n²
= 4M² – M²
= 3M²
Thus, the Mth term of the sequence is \(\frac{n^2}{3 n^2}=\frac{1}{3} .\)

Question 11.
Karim and Genie
Karim was taking a nap under a tree. He had a dream about a magical lamp and a genie. He heard a voice saying, “I have come to serve you,
Oh, master”. He woke up, and to his surprise, it was a Genie!
“Do you want to make money?”, asked the Genie. Karim nodded dumbly in bewilderment. The Genie continued, “Do you see the banyan tree over there? All you have to do is go around it once. The money in your pocket will double”.
Karim immediately started towards the tree, only to be stopped by the Genie. “One moment!” said the Genie. “Since I am bringing you great riches, you should share some of your gains with me. You must give me 8 coins each time you go around the tree.

Thinking that was a trifling amount, Karim readily agreed.
He went around the tree once. Just as the Genie had said, the number of coins in his pocket doubled! He gave 8 coins to the Genie. He made another round. Again, the number of coins doubled. He gave 8 more coins to the Genie.
He went around the tree for the third time. The number of coins doubled again, but to his horror, he was left with only 8 coins, exactly the number of coins he owed the Genie!

As Karim began to wonder how the Genie tricked him, the Genie let out a loud laugh and disappeared.
(i) How many coins did Karim initially have?
(ii) For what cost per round should Karim agree to the deal, if he wants to increase the number of coins he has?
(iii) Through its magical powers, the Genie knows the number of coins that Karim has. How should the Genie set the cost per round so that it gets all of Karim’s coins?
Solution:
(i) Let x be the initial number of coins Karim had.
After the first round, the number of coins doubles, and he gives away to Genie 8 coins.
∴ The number of coins remaining = 2x – 8
Similarly, for the second round,
The number of coins = 2(2x – 8) – 8
= 4x – 16 – 8
= 4x – 24
After the third round,
The number of coins = 2(4x – 24) – 8
= 8x – 48 – 8
= 8x – 56
Since he was left with exactly 8 coins.
∴ 8x – 56 = 8
⇒ 8x = 64
⇒ x = \(\frac{64}{8}\)
x = 8
Hence, Karim initially had 8 coins.

(ii) Let the cost per round be c.
So, the number of coins after one round = 2x – c
For the number of coins to increase, the final amount must be greater than the initial amount.
2x – c > x ⇒ x > c
Karim should agree to the deal if the cost per round is less than 8 coins.

(iii) For the Genie to get all of Karim’s coins, the number of coins remaining after a round must be zero.
∴ 2x – c = 0
⇒ c = 2x
Hence, the Genie should set the cost per second to be exactly twice the number of coins Karim has at the beginning of that round.

Students can use Class 7 Science Curiosity Extra Questions and Chapter 4 The World of Metals and Non metals Extra Question Answer to prepare effectively at home.

Class 7 Science Chapter 4 The World of Metals and Non metals Extra Questions

Class 7 Science Chapter 4 Extra Questions on The World of Metals and Non metals

The World of Metals and Non metals Class 7 Very Short Question Answer

Question 1.
Name two metals.
Answer:
(i) Iron, (ii) Copper.

Question 2.
Name any two non-metals used in daily life.
Answer:
(i) Oxygen, (ii) Carbon.

Question 3.
Give one use of aluminium foil.
Answer:
To wrap food items.

Question 4.
Name the metal used in electrical fittings.
Answer:
Copper.

Question 5.
How malleability benefit everyday life?
Answer:
Malleability allows materials in touseful products like aluminium and silver to be formed foil and decorative sheets.

Question 6.
What does Magnesium Ribbon produce after burning ?
Answer:
Magnesium oxide, due to reaction of oxygen with magnesium in air.

Question 7.
Why is sodium stored in kerosine oil?
Answer:
Because Sodium (Na) reacts with the water and oxygen producing heat, hence kerosine prevents exposure of sodium to air as well as moisture.

Question 8.
Why is phosphorus stored in water?
Answer:
Because the phosphorus catches fire if it is exposed to air in atmosphere.

Question 9.
Oxides of non-metals are acidic or basic?
Answer:
The oxides of non-metals are acidic in nature.

Question 10.
Name some non-metals.
Answer:
Chlorine, sulfur, oxygen, nitrogen, carbon, iodine etc.

Question 11.
Define an element.
Answer:
An element is defined “as a substance that cannot be broken into simpler substances”.

Question 12.
Which property of metals allows them to be drawn into wires?
Answer:
Ductility

Question 13.
Name a non-metal used in water purification.
Answer:
Chlorine
Question 14.
Which non-metal is essential for respiration?
Answer:
Oxygen

Question 15.
Solution of which non-metal is applied on wounds as an antiseptic?
Answer:
Iodine

Question 16.
Name the gas which is formed on burning of sulfur?
Answer:
Sulfur dioxide gas

Question 17.
What do we call the shine present on the surface of metals?
Answer:
Metallic luster

The World of Metals and Non metals Class 7 Short Question Answer

Question 1.
Why are metals essential in daily life ?
Answer:
Metals essential in daily life due to their distinct properties like lustrous nature, high strength, heat and the electrical conductivity etc.

Question 2.
What is the role of carbon and oxygen in everyday life? (V.Imp.)
Answer:
Oxygen is necessary for breathing, we cannot survive without oxygen. The carbon compounds such as fats, carbohydrates and proteins are essential for growth and energy.

Question 3.
What is an alloy? What is its use in our daily life?
Answer:
An alloy is “a mixture of a metal and a nonmetal, two or more metals.” It is necessary for everyday use as in utensils and modern tools and industries, zirconium used in atomic energy and titanium in aerospace.

Question 4.
Name any two substances which behave differently from the metals in air an water. Write their properties also.
Answer:
Phosphorous and sulfur are two non-metals that behave differently in air and water. Mostly they are dull and soft in their appearance. Sulfur forms sulfur dioxide when it burns in air. SO₂ if dissolved in water, forms sulfurous acid. The phosphorus is stored in water because it catches fire when exposed to air in atmosphere.

Question 5.
Sodium metal is kept in kerosene but not water. Why?
Answer:
Sodium is a highly reactive metal. When exposed to air, it starts to burn and forms sodium oxide. Similarly, it reacts vigorously with water. It does not react with kerosene. Therefore, to prevent its exposure to moisture. and air, it is kept in kerosene.

Question 6.
Give one effect of water and one of air on magnesium. (V.Imp.)
Answer:
Magnesium burns in air with a dazzling flame to form a white powder that is magnesium oxide. The reaction takes place between magnesium and oxygen present in atmosphere. Magnesium oxide is basic in nature as it converts red litmus paper to blue.

Question 7.
Phosphorus is kept in water. Why?
Answer:
Generally, non-metals do not react with water, but they may be very reactive in air. Such nonmetals are stored in water; phosphorus is a very reactive non-metal. It catches fire, if exposed in air. To prevent this, it is kept in water.

Question 8.
Prepare a list of some material that are good and poor conductors of electricity.
Answer:
See the list as:
(a) Good conductors of Electricity: An iron nail, a piece of aluminium foil, copper wire, etc.
(b) Poor conductors of Electricity: Peasized lump of the sulfur, a piece of coal, piece of dry wood, a piece of stone, an eraser made by rubber, the small piece of nylon rope plastic covers on screwdrivers, the rubber gloves of an electrician etc.

Question 9.
Which objects show malleability, lusture and hardness ? Name any four.
Answer:
Metals show lusture, hardness and malleability. The objects that once made by copper, iron, aluminium, silver and gold are metals.

Question 10.
(a) Name a metal that occurs in liquid state àt room temperature.
(b) Name some metals that are soft in nature and can be cut by knife.
Answer:
(a) Mercury (used in thermometers)
(b) Metals such as potassium and sodium are soft as well as they are cut by knife.

Question 11.
Compare properties of Metals and Nonmetals.
Answer:
Comparison of Metal and Non-metals:

Metals	Non-metals
1. Hard, shiny in appearance	1. Not hard and dull in appearance
2. Malleable, lustrous, ductile, sonorous	2. Non-malleable, nonlustrous, not ductile and not sonorous
3. Examples : Iron, Gold, Copper and Silver etc.	3. Sulfur and Phosphorous

Question 12.
Compare chemical properties of Metals and Non-metals. (M.Imp.)
Answer:
Comparison of chemical properties of Metals and Non-metals:

Metals	Non-metals
1. Generally form basic oxides with oxygen.	1. They form acidic oxides with oxygen.
2. Form oxides with the water.	2. They do not react with water.
3. Metals react with water.	3. They do not react with water.

Question 13.
Enlist some uses of metals in our daily life.
Answer:
Iron is used to make nails, wires and agricultural tools.
Steel is used to make cromes and the suspension bridges and utensils.
Silver and gold are used to make jewellary ornaments are made from the metal wires.
Copper is used in the electric wires. Aluminium foil is used to pack food. Zinc is used in galvanising of iron. Mercury is used in thermometers.

Question 14.
Define conductors. Write their two categories.
Answer:
Conductors: The materials which transfer heat from one point to the other of a material are conductors of heat e.g., metal spoon and a wooden spoon. Metals are good conductors of heat. Wood remains a poor conductor of heat. Hence, we use metal vessel for heating but their handles are made of wood or some other materials (which do not conduct heat at all).

Question 15.
List four uses of non-metals in everyday life.
Answer:
Phosphorous in used to make fertilizers. Oxygen is used in breathing. Carbon is key component of fats, carbohydrates and proteins. Nitrogen is necessary for plant growth. The chlorine is used in purefication of water. Moreover, iodine solution is used as an antiseptic to be applied on the wounds of a person.

Question 16.
What do you mean by rusting? How can rusting of iron be prevented ?
Answer:
Rusting is “the formation of rust on objects”. e.g., brown deposits or discolouration of an iron nail when put in moist air. It can be prevented by oiling, painting, greasing or by applying a protective layer of zinc metal on the iron. This serious problem causes loss of money that is spent on replacing prepairing iron structures damaged due to it.

Question 17.
Classify elements on the basis of their physical/chemical properties.(Imp.)
Answer:

Question 18.
Write explanatory notes on the following non-metals:
(a) Chlorine
(b) Iodine and
(c) Nitrogen
Answer:
(a) Chlorine: A non-metal, used in water purification.
(b) Iodine: A non-metal, in solution form, this may be used as an antiseptic to cure wounds of persons affected.
(c) Nitrogen: A non-metal, essential for growth of plants. Mostly useful in manufacture of chemicals and the fertilizers also. It is an essential nutrient in plant nutrition.

Question 19.
What do say about the science and society now-a-days?
Answer:
Several metals and alloys are important in daily life in our society for everyday use. Alloy (a mixture of metal and a non-metal, two or more metals etc.) and some metals are essential in modern technology at all. They form a part of an industry. Special metals are used in aerospace and atomic energy. Recycling of iron is done to minize their wastage.

Question 20.
Write note on “wonder of ancient Indian Technology”.
Answer:
Iron pillar of Delhi. It was made in about more than 1600 years ago (time of Chandragupta II). It weights upto 6000 kg with a height of eight meters. It faces open atmosphere, strong winds, intense weather conditions, heavy rainfall. There is no rusting on it now-a-days.

The World of Metals and Non metals Class 7 Long Question Answer

Question 1.
Analyse some objects in reference to malleability, lusture, non-lusture and hammering effect as well as hardness/ softness. (V. Imp.)
Answer:
The piece of copper is lustrous in appearance. It is hard and become flattened on hammering. A piece of coal is non-luctrous, soft and can be broken into pieces on hammering it. A block of wood is soft, non-lustrous but is broken into pieces on hammering. Moreover a piece of aluminium becomes flat on hammering. It is hard and show lusture also. A pea-sized lump of sulfur is soft, shows no lusture and become broken into pieces on hammering.

Question 2.
State the impact of iron on progress of the civilization in our country.
Answer:
Copper and gold are metals which are used to make objects for different purposes like utensils, jewellary, in construction also. The use of iron has significant role in our industry. Iron is used to make agricultural tools. It has significant role in our civilization.

Question 3.
Write a note on sonority of metals.
Answer:
Sonority refers “to the ringing sound production by a metal.”
Examples of it are ringing sound of ghungurus, sound of a school bell. They are due to sonority of metals. Other examples are ringing sounds produced by a metal spoon or metal coin. Dull sounds are produced by wood and coal objects.

Question 4.
What is corrosion of metals ? How it can be prevented? (Imp.)
Answer:
The corrosion refers “to a process by which the materials like metals are slowly eaten away if these are exposed to air and water.” It is discolouring of metal surface gradually by air and water. You must have seen green coating on surface if copper object, even a black coating on the surface of silver objects. It occurs when objects are kept in open atmosphere. It causes heavy losses to us. It is wasteful and troublesome process. Gold does not corrode in open air.

Question 5.
Take some amount of sulfur. Perform an experiment with it to show its burning. Analyse the result also. (V. Imp.)
Answer:
Take some amount of sulfur. Make its powder in pestle by a mortal. Take it in a deflagrating spoon. Heat this on a flame. Put it in a gas jar. Cover the gas jar by a lid tightly. Take the product formed out of jar. Analyse it. Sulfur burns in air or oxygen to form sulfur dioxide gas.

Question 6.
Describe the process of rusting and its prevention methods, with examples.
Answer:
Rusting is a chemical reaction where iron reacts with oxygen and moisture in the air, forming reddish-brown rust, which weakens iron objects like tools or bridges. It requires both air and water; iron does not rust in dry air or water alone. Prevention methods include:
a. Painting: Coating iron with paint, e.g., painting bridges to block air and moisture.
b. Oiling/Greasing: Applying oil, e.g., greasing bicyle chains to form a protective layer.
c. Galvanisation: Coating with zinc, e.g., galvanised iron buckets to prevent rust. These methods protect iron structures, saving costs on repairs and ensuring safety, as rust makes objects weak and unsafe.

The World of Metals and Non metals Class 7 Case Based Questions

1. Read the following passage carefully and answer the questions that follow:
Non-metals are essential in our daily life due to their distinct properties. They are not lustrous. They do not show malleability and ductility also. They are poor conductors of heat and electricity. Examples are oxygen, iodine, carbon, nitrogen etc.

(i) What are non-metals?
(a) They are lustrous
(b) They show malleability
(c) They exhibit ductily
(d) None of these
Answer:
(d) None of these

(ii) What are properties of non-metals?
(a) They are non-lustrous
(b) They do not show ductility
(c) They do not exhibit malleability
(d) All of these
Answer:
(d) All of these

(iii) Non-metals essential in our everyday life are:
(a) Carbon is essential to grow
(b) Oxygen is essential in breathing
(c) Nitrogen is a necessary element for growth of a plant
(d) All of these
Answer:
(d) All of these

2. Read the following passage carefully and answer the questions that follow: properties of metals, such as ductility, sonority, heat conduction, and electrical conductivity. They dipped metal and wooden spoons into hot water and checked which spoon got hotter. They also dropped a metal coin and a wooden block to hear the sound. In another experiment, they used a tester circuit to see if the materials conducted electricity.

(i) Why did the metal spoon become hotter than the wooden spoon in hot water?
(a) Metal reacts with hot water
(b) Metal is a poor conductor of heat
(c) Metal is a good conductor of heat
(d) Wooden spoons absorb water
Answer:
(c) Metal is a good conductor of heat

(ii) What property of metals allows them to produce a ringing sound when dropped?
(a) Malleability
(b) Conductivity
(c) Sonority
(d) Elasticity
Answer:
(c) Sonority

(iii) Which of the following materials would cause a bulb to glow in a tester circuit?
(a) Plastic rod
(b) Iron nail
(c) Rubber band
(d) Nylon rope
Answer:
(b) Iron nail

(iv) Why is rubber used in the handles of tools used by electricians?
(a) It is shiny and attractive
(b) It is soft and comfortable
(c) It is a poor conductor of electricity
(d) It reacts with metals
Answer:
(c) It is a poor conductor of electricity

The World of Metals and Non metals Class 7 Picture Based Questions

1. Look at the picture and answer the following questions:

(i) Which property of metal is conducting through activity?
(a) Ductility
(b) Malleability
(c) Sonority
(d) None of these
Answer:
(b) Malleability

(ii) Which property allows a metal like iron to be flattened into sheets when beaten?
(a) Ductility
(b) Brittleness
(c) Malleability
(d) Elasticity
Answer:
(c) Malleability

(iii) What are the essential conditions for rusting?
Answer:
(i) Presence of moisture (water)
(ii) Presence of air (oxygen)

The World of Metals and Non metals Extra Questions for Practice

Multiple Choice Questions (MCQs):

Question 1.
The good conductors of heat and electricity are:
(a) metals
(b) non-metals
(c) none of these
(d) all of these

Question 2.
The most malleable metals are:
(a) Gold
(b) Silver
(c) Both (a) and (b)
(d) All of these

Question 3.
The ornaments made from wires of metals are:
(a) Earrings
(b) Bangles
(c) Necklaces
(d) All of the above

Question 4.
Select the metal:
(a) Oxygen
(b) Phosphorous
(c) Sulfur
(d) Iron

Question 5.
Material which can be drawn into wires is:
(a) Gold
(b) Carbon
(c) Oxygen
(d) Coal

Very Short Answer Type Questions:

Question 1.
What are metals?

Question 2.
How can we prevent rusting of iron?

Question 3.
How plastic covering of rubber gloves protect electrician from the electric shock?

Question 4.
Name a soft metal.

Question 5.
A material can be drawn into thin wires, it is said to be a _______.

Short Answer Type Questions-I:

Question 1.
What do you mean by malleability ? Give an example of material that shows it.

Question 2.
Give on main use of iron.

Question 3.
Why phosphorous is stored in water?

Question 4.
Rusting of iron is a serious problem. Why?

Question 5.
Magnesium oxide is acidic, basic or neutral in nature. Which one is correct among these?

Question 6.
Presence of air and water are essential for formation of rust on a metal or iron nail. Make an experiment to prove it.

Question 7.
Differentiate in the sound produced by a metal spoon, a block of wood and a piece of coal.

Question 8.
Give the meaning and examples of:
(a) Malleability
(b) Ductility and
(c) Sonority

Question 9.
By an experiment show reaction of a non-metal with oxygen. Say a non-metal may be a piece of sulfur.

Question 10.
Give some uses of iron and copper.

Long Answer Type Questions:

Question 1.
Explain corrosion of metals by giving an example.

Question 2.
Show rusting of iron nail by an experiment and figures.

Question 3.
(a) Name some metals.
(b) Plastic, wood, rubber, paper are metals or non-metals. Explain briefly.

Question 4.
Why are alloys important for daily use?

Students can use Class 7 Science Curiosity Extra Questions and Chapter 3 Electricity Circuits and Their Components Extra Question Answer to prepare effectively at home.

Class 7 Science Chapter 3 Electricity Circuits and Their Components Extra Questions

Class 7 Science Chapter 3 Extra Questions on Electricity Circuits and Their Components

Electricity Circuits and Their Components Class 7 Very Short Question Answer

Question 1.
Name an insulator made of wood.
Answer:
Stick.

Question 2.
Is key made up of metal is a good conductor of electricity.
Answer:
Yes.

Question 3.
Why wires are covered with plastic?
Answer:
The plastic is electrical insulator.

Question 4.
Name some components of a simple electric circuit.
Answer:
Battery, wire, key and bulb are the components of a simple electric circuit.

Question 5.
Electric lamps are of two types. Name them.
Answer:
(a) LED lamp (b) Incandescent lamp.

Question 6.
Why wires made of copper are used in electric cisuits?
Answer:
Copper is a good conductor of electricity and a less costly metal.

Question 7.
Does the bulb glow when the circuit is open?
Answer:
No, the bulb does not glow if circuit is open.

Question 8.
What is direction of electric current in an electric circuit?
Answer:
Positive to the negative terminal of an electric cell.

Question 9.
Draw symbol for an electric lamp.
Answer:

Question 10.
What type of electricity is used in homes and industries?
Answer:
Alternating Current (AC)

Question 11.
What happens if the filament in an incandescent lamp breaks?
Answer:
The lamp stops glowing because the circuit is broken.

Question 12.
Which component of a torchlight is powered by the battery to provide light?
Answer:
LED or Incandescent lamp.

Question 13.
The safety pin touches two drawing pins to close gaps, to complete path and permit the current to flow. What do you call this position?
Answer:
“ON” Position.

Question 14.
Name a device that completes or breaks the circuit. What do you use for lights?
Answer:
Switches of different designs.

Question 15.
What happens when an electric cell is connected to a circuit?
Answer:
It supplies electrical energy to the circuit.

Electricity Circuits and Their Components Class 7 Short Question Answer

Question 1.
Define a circuit diagram.
Answer:
It is defined “as a representation of electrical circuit by use of symbols”.

Question 2.
Distinguish between Incandescent lamp and LED lamp.
Answer:
Following are the difference

Incandescent Lamp	LED Lamp
1. It has a filament.	1. It does not have a filament.
2. Torchlight is used in these lamps.	2. A torch can use one or more LED’s.

Question 3.
Draw a circuit diagram for LED lamp.
Answer:

Question 4.
Compare a scale to a key in reference to good or bad conductors of electricity.
Answer:
Difference between a scale and a key:

A Scale	А Кеу
1. Made of wood/plastic.	1. Made of metal.
2. Insulator of electricity.	2. Conductor of electricity.

Question 5.
Differentiate between Conductors and Insulators of electricity.
Answer:
The difference are:

Conductor	Insulator
1. Good conductor of electricity.	1. Poor conductor of electricity.
2. e.g., ceramics	2. e.g., plug tops.

Question 6.
(a) Name portable source of electrical energy.
(b) Two terminals of an electric cell are. Name them.
Answer:
(a) Electrice cell.
(b) positive and negative terminals.

Question 7.
Draw a circuit diagram of an electrical circuit with an incandescent lamp.
Answer:

Question 8.
Explain an electrical circuit with the help of a diagram.
Answer:

This shows a complete path of electric current to flow through a lamp. When current passes through a circuit, the lamp glows then. This makes an electrical circuit one terminal of an electric cell is united to the other terminal of a lamp. See figure.

Question 9.
Expand the following :
(a) IEC
(b) IEEE
Answer:
(a) IEC: International Electro-chemical Commission.
(b) IEEE: Institute of Electrical and Electronics Engineers.

Question 10.
How can we connect the cells to prepare a battery?
Answer:
The positive terminal of one cell is connected to the negative terminal of the next cell to prepare a battery.

Question 11.
Draw the symbol of an electric bulb in an electric circuit.
Answer:

Question 12.
How do you make an electric lamp glow by using an electric cell?
Answer:
(a) Take four lengths of a wire, a torch, lamp, an electric cell and a cell holder. Then remove plastic cover app. 1 cm but both ends of each wire must be clear. Now, unite two wires to two ends of the cell holder.

(b) Insert cell into holder, -ve terminal lies on spring side.

(c) Two wires to screws of lamp holder are not attached. In holder, fix the lamp then (turn it around in a holder). After all you unite a cell to lamp for glowing.

Question 13.
Draw a figure of an LED lamp for a torch.
Answer:

Question 14.
Construct LED’s for different colours. Does LED has filaments ? Explain shortly.
Answer:
See figure as given below of LED’s.

The LED’s do not have filaments but possess two terminals (+ve and -ve); +ve remain united to -ve one.

Question 15.
Explain the construction of a battery.
Answer:
A battery is a combination of two or more cells.
It is constructed by placing the cells properly in a cell holder so that the positive terminal of one cell is connected to the negative terminal of the next cell. A metal wire is then connected to each of the two metal.

Question 16.
(a) Draw circuit diagrams of a cell and an LED.
(b) Draw circuit figures with an incandescent lamp and an LED lamp.
Answer:
(a) See figure

(b) See figure

Question 17.
Construct figures of conduction tester and the use of it to test a material.
Answer:
See following figure as in Q.no. 5 LA type.

Question 18.
Prepare a list of five insulators as well as conductors of electricity. Name object, material it made of and write conclusion (whether conductor or insulator).
Answer:
List of Insulators/Conductors (five) :

S. No.	Object	Material	Conclusion
1.	Eraser	Rubber	Insulator
2.	Key	Metal	Conductor
3.	Candle	Wax	Insulator
4.	Scale	Plastic	Insulator
5.	Stick	Wood	Insulator

Question 19.
Compare good conductors and poor conductors of electricity by giving examples of each. (V.Imp.)
Answer:
The comparison are :

Good Conductors	Poor Conductors
1. These are materials by which electricity may flow.	1. Materials by which electric current does not flow.
2. These are good conductors of electric current.	2. They are bad conductors of electricity.
3. Examples are copper, silver.	3. Examples are candle made of wax and eraser made by rubber.
4. Socket is made of wires/conductors to protect people.	4. Plastic insulator protect us from electric shock at all.

Question 20.
Draw a well-labelled diagram of small incandescent lamp that may be used in a torch.
Answer:
See figure :

Question 21.
Why should we not touch the lighted bulb?
Answer:
We should never touch a lighted electric bulb connected to the mains because it may be very hot, and touching it could result in serious burns. Similarly, we should avoid experimenting with electrical supplies from the mains, a generator, or an inverter, as they may cause an electric shock.

Question 22.
Draw the symbols of the following circuit components.
(i) electric cell
Answer:

(ii) Switch in ‘OFF’ position
Answer:

(iii) electric bulb
Answer:

(iv) battery
Answer:

Electricity Circuits and Their Components Class 7 Long Question Answer

Question 1
Define electric circuit with the help of diagram.
Answer:
A simple electrical circuit is shown by an electric cell. See figure an electric cell has ‘+ve’ and ‘-ve’ terminals as shown by marks on a cell. Electric cell possesses two terminals – one is ‘+ve’ and other is -ve. Positive terminal is a metal cap. But metal disc shows ‘-ve’ terminal of electric cell at all. The portable source of electrical energy is shown by an electric cell now-a-days.

Question 2.
Show a battery of two cells as well as a battery of 4 cells. Now cells one united in a battery. (Imp.)
Answer:
Battery: A battery is a device formed by connecting two or more cells together. To form a battery, the cells are placed in a cell holder so that the positive terminal of one cell is connected to the negative terminal of the next cell, and so on. A metal wire is connected to each of the two metal clips on the cell holder.

Question 3.
Define a circuit diagram. Write electric components and draw their symbols.
Answer:
See circuit diagrams given below as :

Question 4.
Construct circuit figure to show switch on and switch off positions by symbols.
Answer:
Switch on, switch off positions and symbols. See figure :

Question 5.
Connect a lamp to an electric cell. Leave the two ends of wires un-united. Use a conduction tester for testing a material. Show these by diagrams. Write procedure.
Answer:
Lamp, Electric cell and A Tester : Procedure : Connect a lamp to an electric cell. Leave 2 ends of connection open. Use a tester say metal spoon to test the material through which current passes.

Electricity Circuits and Their Components Class 7 Case Based Questions

1. Read the following passage carefully and answer the questions that follow :

We use fuse to check electric current. To save electric appliances to get damaged from excessive flow of electric current. We use a safety device. It is known as fuse. It prevents big amount of current from flowing in a device appliance since it cuts off supply of electricity, hence prevents damage. It has a wire made of material. That melts easily if heated. It breaks a circuit hence stops flow of current in a circuit.

(i) Device used to prevents flow of excessive current in the circuit is known as :
(a) fuse
(b) bulb
(c) switch
(d) None of these
Answer:
(a) fuse

(ii) The lamp is fused. The reason is a broken :
(a) lamp
(b) filament
(c) wire
(d) current flow
Answer:
(b) filaments

2. Read the following passage carefully and answer the questions that follow :

In a classroom activity, students were given wires, a bulb, a switch, and a cell. They connected the components to form a circuit, but the bulb didn’t glow. They examined the setup and discovered that one of the wires was broken. After replacing it, the bulb glowed brightly. Their teacher asked questions about the flow of current, the role of conductors, and why a complete path is needed.

(i) What is the most likely reason the bulb did not glow initially?
(a) The bulb was faulty
(b) The cell was too weak
(c) The wire was broken
(d) The switch was open
Answer:
(c) The wire was broken

(ii) What is required for an electric current to flow in a circuit?
(a) A plastic wire
(b) An open switch
(c) A complete and closed path
(d) A glowing bulb
Answer:
(c) A complete and closed path

(iii) What is the function of a switch in an electric circuit?
(a) To control the brightness of the bulb
(b) To increase the voltage
(c) To open or close the circuit
(d) To connect the bulb to the wire
Answer:
(c) To open or close the circuit

(iv) Which of the following materials would best replace the broken wire?
(a) Cotton thread
(b) Rubber strip
(c) Copper wire
(d) Plastic tube
Answer:
(c) Copper wire

Electricity Circuits and Their Components Class 7 Picture Based Questions

I. Observe the picture and answer the questions :

Question 1.
The circuit must be closed to:
(a) cell to operate
(b) glow bulb
(c) stop circuit
(d) current to glow
Answer:
(d) current to glow

Question 2.
Bulb will glow only when current is flowing through
(a) circuit
(b) battery
(c) cells
(d) bulb
Answer:
(a) circuit

Question 3.
What is thin wire called and when it glows?
Answer:
A thin wire is called a filament and it glows when electric current passes through it.

II. Observe the picture and answer the following questions :

Question 1.
What does the above given image show?
(a) An electric cell
(b) A battery
(c) A power house
(d) None of these
Answer:
(a) An electric cell

Question 2.
What is the terminal marked with a “+” sign called?
(a) Negative terminal
(b) Positive terminal
(c) Both of these
(d) None of these
Answer:
(b) Positive terminal

Question 3.
Which terminal of the cell does the electric current flow from?
(a) Positive terminal
(b) Negative terminal
(c) Only (b) is correct
(d) None of these
Answer:
(a) Positive terminal

Question 4.
What is the function of the positive and negative terminals in an electric cell?
Answer:
The positive and negative terminal in an electric cell help to create path for flow of current.

Electricity Circuits and Their Components Extra Questions for Practice

Multiple Choice Questions (MCQs):

Question 1.
Electricity is used in :
(a) lighting
(b) transportation
(c) cooking
(d) all of these

Question 2.
A simple circuit is represented by :
(a) Electric cell
(b) Insulators
(c) Conductors
(d) None of these

Question 3.
An incandescent lamp does not glow even it remain united to a cell :
(a) Lamp is fused
(b) Filament of lamp is broken
(c) Flow of current is stopped
(d) All of the above

Question 4.
Which is used to test electrical experiments?
(a) Cells
(b) Wall clocks
(c) Batteries
(d) All of these

Very Short Answer Type Questions:

Question 1.
What is torchlight?

Question 2.
Draw symbol for an electric cell.

Question 3.
What is meant by “circuit is open”?

Question 4.
What does the two lines represent in a symbol of electric cell?

Short Answer Type Questions:

Question 1.
Name any three poor conductors of electricity.

Question 2.
Name any three good conductors of the electricity.

Question 3.
Draw a closed circuit.

Question 4.
State three symbols each for (i) electric lamp, (ii) an LED, (iii) a battery.

Question 5.
Draw a diagram to show an electric lamp.

Question 6.
Draw an Electrical Circuit.

Question 7.
Write short notes on :
(a) battery
(b) fuse
(c) switch

Question 8.
How will you use a conduction tester to test a material like a steel spoon?

Long Answer Type Questions :

Question 1.
Insulators protect us from electric shocks. How?

Question 2.
Why should we handle electrical appliances with care? Explain briefly.

Question 3.
How would you make a torch lamp to glow by using a battery?

Question 4.
Write explanatory notes on :
(a) A Torchlight
(b) An Electric cell
(c) A Battery
(d) An LED