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.