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Class 8 Science Chapter 7 Particulate Nature of Matter Extra Questions
Class 8 Science Chapter 7 Extra Questions on Particulate Nature of Matter
Particulate Nature of Matter Class 8 Very Short Question Answer
Question 1.
What is the smallest unit of matter that retains the identity of the substance?
Answer:
The smallest unit of matter is called a constituent particle, which makes up a substance and retains all its original properties even when broken down further.
Question 2.
A chalk stick appears smooth to the eye, but when it is scratched or broken, a fine powder is seen. How does this observation support the particulate nature of matter?
Answer:
This observation shows that even seemingly continuous materials are made up of tiny particles. When scratched, the particles separate and prove that matter is made of small particles.
Question 3.
Riya added salt to water and stirred it. The solution looked clear with no visible salt. What does this tell us about the size and movement of particles?
Answer:
The salt particles are very small and get evenly distributed between water particles. This indicates that matter is made of tiny particles that can mix and move.
Question 4.
What do we mean by interparticle space?
Answer:
Interparticle space refers to the tiny gaps between the particles of a substance that allow particles of another substance to settle in.
Question 5.
Why do solid particles only vibrate and not flow like liquids or gases?
Answer:
Solid particles have very strong interparticle attractive forces and low thermal energy, so they remain tightly packed and can only vibrate in place.
Question 6.
Give reason as why does the water level not rise after sugar dissolves in it?
Answer:
The water level does not rise after sugar dissolves in it because sugar particles fill the spaces between water molecules instead of adding to the total volume, so the level remains the same or lowers slightly.
Question 7.
Which ancient philosopher introduced the idea of “Parmanu”?
Answer:
Acharya Kanad, an ancient Indian philosopher was the first who proposed that matter is made up of indivisible particles called “Parmanu”, or atoms.
Question 8.
Why do solids have a fixed shape?
Answer:
Solids have a fixed shape because their particles are tightly packed and held by strong forces that prevent them from moving freely.
Question 9.
When a solid changes into a liquid at its melting point, what happens to the attractive forces between the particles? (Competency Based Que.)
Answer:
At the melting point, thermal energy increases, and it weakens the attractive forces between solid particles, allowing them to move more freely and convert into a liquid.
Question 10.
What does it mean if a substance has a definite volume but no fixed shape?
Answer:
It means the substance is a liquid, which maintains a fixed amount of space but adapts to the shape of its container.
Question 11.
Why does potassium permanganate spread faster in hot water?
Answer:
Heat increases the motion of water particles, allowing the color particles to spread more rapidly throughout the liquid.
Question 12.
Why do gases occupy the entire space of a container?
Answer:
Gases occupy the entire space of a container because their particles are far apart, move freely in all directions, and spread out to fill all available space.
Question 13.
What happens when gas particles are compressed in a syringe?
Answer:
The gas particles are pushed closer together, reducing the volume, which shows that gases are compressible due to large spaces between particles.
Question 14.
Ravi accidentally left the cap of his perfume bottle open in one corner of the room. Within minutes, the entire room started smelling of the perfume. Based on the nature of matter, explain why this happened. (Competency Based Que.)
Answer:
This happened because particles of the perfume are in constant motion and have large intermolecular spaces. They diffuse into the air and spread throughout the room, which is a property of gases.
Question 15.
When sand is added to water, it settles down without mixing. What does this suggest about sand particles?
Answer:
Sand particles are too large and insoluble in water, so they do not occupy spaces between water particles or dissolve.
Particulate Nature of Matter Class 8 Short Question Answer
Question 1.
How do interparticle attractions influence the physical state of a substance, and what role does the distance between particles play in this? (Competency Based Que.)
Answer:
The strength of interparticle attractions determines whether a substance exists as a solid, liquid, or gas. When the particles are close together, the attractive forces are strong, keeping the substance in a solid or liquid state. If the distance between particles increases, these forces become weaker, which can lead the substance to change into a gaseous state.
Question 2.
When a solid is heated, its particles start vibrating faster. After some time, the solid melts. What does this tell us about the relationship between heat and interparticle forces?
Answer:
Heating increases the movement of particles. As they vibrate more strongly, the forces holding them together become weaker. When these forces can no longer hold the particles in fixed positions, the solid changes into a liquid.
Question 3.
The melting points of ice, urea, and iron are 0°C, 133 °C, and 1538°C, respectively. What can you conclude about the strength of interparticle forces in these solids based on their melting points? Support your answer with one example from the table. (Competency Based Que.)
Answer:
Solids with lower melting points have weaker interparticle forces, while those with higher melting points have stronger forces. For example, ice melts at 0°C, showing that it has weak interparticle attraction, while iron melts at 1538°C, indicating very strong interparticle forces.
Question 4.
Rina heated water in a vessel and noticed that bubbles started forming only after a certain temperature Was reached. (Competency Based Que.)
(i) What is the name of this specific temperature at which bubble formation begins?
(ii) Why do bubbles form inside the liquid only at this temperature and not before?
Answer:
(i) The temperature is called the boiling point of the liquid.
(ii) At the boiling point, the particles of the liquid move fast enough to break free from the attraction between them and form vapour, which appears as bubbles inside the liquid.
Question 5.
Water spilled on the floor disappears after some time, even when it is not hot. What does this observation tell us about the movement of particles in liquids and gases?
Answer:
This shows that the particles in a liquid can slowly leave the surface and mix with air particles. It also indicates that gas particles are always moving and have space between them, allowing water particles to spread into the air.
Question 6.
“Gases are highly compressible, but solids are not.” Justify this statement using the arrangement of particles.
Answer:
Gases are compressible because their particles are far apart with large empty spaces, allowing external pressure to push them closer whereas solids have tightly packed particles with negligible intermolecular space that make them incompressible.
Question 7.
Give reasons for the following statements.
(i) Liquids flow but solids do not.
(ii) A gas fills the entire space of its container.
Answer:
(i) Liquids flow because their particles can slide past each other due to weaker interparticle forces than solids.
(ii) Gases fill the container because their particles move freely at high speed in all directions.
Question 8.
Solid iodine kept in a closed gas jar slowly changes into vapour and spreads to fill the entire space.
(i) What does this observation tell us about the movement of particles in gases?
(ii) Why does the iodine vapour spread to fill the entire jar on its own?
Answer:
(i) It shows that gas particles move freely in all directions and occupy all available space.
(ii) Iodine vapour spreads on its own because gas particles are not tightly packed and can move freely.
Question 9.
Classify the following substances into solids, liquids and gases.
(Salt, Oil, Nitrogen, Stone, Vinegar, Carbon dioxide)
Answer:
These substances can be classified as follows
| Solid | Liquid | Gas |
| Salt | Oil | Nitrogen |
| Stone | Vinegar | Carbon dixoide |
Question 10.
The word ‘particle’ is used in both science and everyday language. How is the meaning of ‘particle’ in Suspended Particulate Matter (SPM) different from its meaning in the concept of particulate nature of matter? (Competency Based Que.)
Answer:
In Suspended Particulate Matter (SPM), the term ‘particle’ refers to very tiny dust or smoke particles that are suspended in air and can sometimes be seen with the naked eye or under a microscope. These are still large compared to the particles described in the particulate nature of matter. In science, when we talk about the particulate nature of matter, ‘particles’ mean the extremely small building blocks of matter i.e„ atoms or molecules, that are much smaller than dust and cannot be seen even under a microscope.
Particulate Nature of Matter Class 8 Long Question Answer
Question 1.
(i) Explain why solids have a definite shape and volume, while gases do not, based on the arrangement of particles.
(ii) How does the spacing between particles differ in solids, liquids, and gases?
Answer:
(i) Solids have a definite shape and volume because their particles are tightly packed in a fixed arrangement with strong intermolecular forces, restricting movement. In contrast, gas particles are far apart which can easily move freely and have weak forces that allow them to expand and fill any container.
(ii) The difference between spacing of particles is as follows
- Solids : Particles are very close together (minimal spacing).
- Liquids : Particles are slightly farther apart (moderate spacing).
- Gases : Particles are widely spaced (maximum spacing).
Question 2.
Give two examples each of solid, liquid, and gas substances that you have seen around you. Also mention one property shown by each example that helps you identify its state as solid, liquid or gas.
Answer:
| State of Matter | Examples | Property observed |
| Solid | (i) Stone | Has a fixed shape and volume. |
| (ii) Salt | Cannot be compressed and retains its shape even when kept in a bowl. | |
| Liquid | (i) Water | Takes the shape of the container but has a fixed volume. |
| (ii) Milk | Can flow and be poured, but does not have a fixed shape. | |
| Gas | (i) Oxygen | Cannot be seen, fills the entire space in a room or a container. |
| (ii) Steam | Spreads in all directions and does not have a fixed shape or volume. |
Question 3.
Ankush observed that water in a glass tumbler remains at the same level even if the shape of the glass is changed. Later, he noticed that some water spilled on the table disappeared after some time, even though the room was not very warm. Based on these observations, answer the following: (Competency Based Que.)
(i) Why does water take the shape of any container?
(ii) What does the unchanged volume tell us about the nature of liquids?
(iii) Why was Ankush able to move his finger through water easily, but not through a solid object like wood?
(iv) Why does water disappear from the table even without boiling?
(v) How is evaporation different from boiling?
Answer:
(i) Water takes the shape of a container because the particles in a liquid can move freely and are not fixed in place, the liquid takes the shape of the container.
(ii) It shows that liquids have a fixed volume, as their particles stay close together even while moving.
(iii) Liquids have weaker interparticle attraction than solids, so particles can move aside when we move a finger through them.
(iv) Water disappears due to evaporation, where particles from the surface slowly escape into the air.
(v) Evaporation happens at all temperatures and only from the surface, while boiling occurs at a fixed temperature and throughout the liquid, forming bubbles.
Question 4.
Observe the diagram showing three states of matter (A, B, C). Identify and label each state based on particle arrangement: (Competency Based Que.)
Answer:
A shows liquid arrangement : The particles are close to each other but not in fixed positions, allowing movement within a limited space.
B shows solid arrangement : The particles are tightly packed in a fixed and orderly manner and showing strong interparticle attraction.
C shows gas arrangement : The particles are far apart and move freely in all directions, indicating very weak interparticle forces.
Question 5.
Give five everyday examples that show how the particulate nature of matter helps to explain physical changes or behaviours.
Answer:
The particulate nature of matter is seen in many everyday situations such as
- Air fills a balloon because gas particles move freely and exert pressure in all directions.
- Sugar dissolves in water as its small particles fit into the spaces between water particles.
- Soap removes oil stains by interacting with both water and oil particles, lifting the oil from the fabric.
- The fragrance of an incense stick spreads across a room because gas particles move quickly and mix with air.
- Salt disappears in water because its particles break apart and mix with water particles.
Particulate Nature of Matter Class 8 Case Based Questions
Question 1.
During an experiment, Arjun added two teaspoons of salt to a glass of water. Initially, the salt settled at the bottom. After stirring, the salt completely disappeared. He repeated the experiment with hot water and noticed that salt dissolved faster. (Competency Based Que.)
(i) Why did the salt disappear in water after stirring?
(ii) What does this experiment prove about the particles of matter?
(iii) Why did salt dissolve faster in hot water?
Answer:
(i) The salt broke into tiny particles and occupied spaces between water particles.
(ii) It shows that matter is made of tiny particles that have space between them.
(iii) Heat increases the movement of water particles, so salt dissolves faster.
Question 2.
A student was asked to place 200 mL of water in three containers of different shapes- cylindrical, conical, and cuboidal. In each case, the water level was up to the same 200 mL mark but the shape changed according to the container. (Competency Based Que.)
(i) What does this activity show about the shape of liquids?
(ii) Did the volume of water change in any container? Why or why not?
(iii) Which property of liquids is demonstrated here?
Answer:
(i) This activity shows that liquids take the shape of the container in which they are poured.
(ii) No, the volume remained constant at 200 mL in all containers.
(iii) Liquids have a definite volume but not fixed shape.
Question 3.
Manik lit an incense stick in one corner of the room. After a while, students sitting on the other side of the room started smelling the fragrance, even though the stick was far away. (Competency Based Que.)
(i) What does this observation suggest about the nature of gas particles?
(ii) Which property of gases allows the fragrance to reach all corners?
(iii) What is the role of air particles in this phenomenon?
Answer:
(i) This observation shows that gas particles move freely and in all directions.
(ii) Gases do not have a fixed shape or volume and occupy all available space.
(iii) Air particles are in constant motion and help spread the fragrance by colliding with it.
Skill Based Questions
Question 1.
A student set up an experiment using a beaker and ice cubes, which were slowly heated using a Bunsen burner. As the heating continued, the student noticed visible changes in the form and behavior of the substance inside the beaker. Observations were carefully noted at each stage. The experiment aimed to study the effect of heat on matter. All safety precautions were followed during the activity. (Experimental Skill)
Answer the following questions.
(i) Identify the states of matter observed during the activity and mention the physical processes responsible for these changes.
(ii) What do these changes tell us about the effect of heat on particle arrangement and motion?
(iii) Arrange the three states observed (solid, liquid, gas) in increasing order of interparticle force of attraction.
Question 2.
While cooking in the kitchen, a student observes that butter kept on the hot pan slowly starts melting and turns into a liquid. The same butter remains solid when left on the kitchen counter. The student wonders why the butter changes its form only when heated and what role temperature plays in this change of state. This real-life observation leads to a deeper curiosity about how solids behave when heat is applied. (Observational Skill)
Answer the following questions.
(i) What does the change in the state of butter tell us about the effect of temperature on solids?
(ii) Why does the butter remain solid at room temperature but melt on the hot pan?
(iii) What does this case suggest about the arrangement and attraction between particles during melting?
Question 3.
On a warm summer day, a person sprays a small amount of perfume in one corner of a closed room. Within moments, the fragrance spreads across the room and is noticed by others sitting at a distance. This everyday-event raises interesting questions about how substances behave in air and how particles interact without direct contact. (Experimental Skill)
Answer the following questions.
(i) What does this observation tell us about the nature of gas particles?
(ii) How does this example support the idea of movement of particles in air?
(iii) What does this activity show about the presence of space between particles of matter?
The Invisible Living World Beyond Our Naked Eye Extra Questions for Practice
Very Short Answer Type Questions
Question 1.
The constituent particles of matter are held together through which type of forces that are attractive in nature?
Question 2.
What do you observe when sugar dissolves completely in water?
Question 3.
Which state of matter allows particles to move the most freely?
Question 4.
What term is used for the invisible forces between particles of matter?
Short Answer Type Questions
Question 1.
When a crystal of potassium permanganate is added to water, the entire solution turns purple. What does this observation tell us about particle movement?
Question 2.
Why do solids generally have higher melting points than liquids or gases?
Question 3.
A balloon expands when air is blown into it. Explain this using the particle nature of matter.
Long Answer Type Questions
Question 1.
Give two examples each of solids, liquids, and gases that you observe at home. Also, mention one property for each state based on particle arrangement.
Question 2.
Describe the changes in particle arrangement and energy when a solid is heated until it becomes a gas. Mention the role of heat in this transformation.