Particulate Nature of Matter – Important Questions and Answers
Premium CBSE Class 8 Science revision post based on the chapter Particulate Nature of Matter. Includes important keywords, very short answers, short answers, long answers, case studies, assertion-reason questions, competency-based questions, HOTS, diagram-based questions, FAQs, and an interactive quiz.
Short Introduction
Matter around us may appear continuous, but it is actually made up of extremely small particles. These particles have spaces between them, attract each other, and are always in motion. The way these particles are arranged and how strongly they attract one another decide whether a substance exists as a solid, liquid, or gas.
Chapter Overview
Matter is Particulate
Matter is made up of extremely small constituent particles that cannot be seen with ordinary microscopes.
Interparticle Spaces
Particles of matter have empty spaces between them. Dissolved sugar occupies spaces between water particles.
Interparticle Attraction
Particles are held together by attractive forces called interparticle attractions.
States of Matter
Solids, liquids, and gases differ in particle spacing, attraction, and movement.
Change of State
Heating increases particle motion and can change solids into liquids and liquids into gases.
Particle Motion
Particles are always moving. Their motion increases when heat is provided.
Important Keywords with Meanings
| Keyword | Meaning |
|---|---|
| Matter | Anything that has mass and occupies space. |
| Constituent particles | The basic tiny units that make up a substance or material. |
| Physical change | A change in which no new substance is formed, such as grinding chalk. |
| Interparticle spaces | The empty spaces present between particles of matter. |
| Interparticle attractions | Attractive forces that hold particles of matter together. |
| Solid | A state of matter with definite shape and definite volume. |
| Liquid | A state of matter with definite volume but no fixed shape. |
| Gas | A state of matter with no fixed shape and no fixed volume. |
| Fluid | A substance that can flow. Liquids and gases are fluids. |
| Melting | Conversion of a solid into a liquid on heating. |
| Melting point | The minimum temperature at which a solid melts into a liquid at atmospheric pressure. |
| Boiling | Fast conversion of a liquid into vapour throughout the liquid at its boiling point. |
| Boiling point | The temperature at which a liquid boils and turns into vapour at atmospheric pressure. |
| Evaporation | Slow formation of vapour from the surface of a liquid at temperatures below boiling point. |
| Vapour | Gaseous form of a substance that is usually liquid or solid at ordinary conditions. |
| Compressibility | Ability of a substance to reduce its volume under pressure. |
| Incompressible | Property of a substance that cannot be compressed easily, such as water. |
| Soluble substance | A substance that dissolves in a liquid, such as sugar in water. |
| Insoluble substance | A substance that does not dissolve in a liquid, such as sand in water. |
| Thermal energy | Heat energy of particles that affects their movement and state of matter. |
| Diffusion | Spreading of particles from one region to another due to their motion. |
| Atom | An extremely small particle of matter; introduced as a higher-grade concept in the chapter. |
| Molecule | A stable particle formed when atoms combine, such as a water molecule. |
| Parmanu | Ancient Indian idea of tiny indivisible particles described by Acharya Kanad. |
Very Short Answer Questions
1. What is matter made up of?
Answer: Matter is made up of extremely small particles.
2. What are constituent particles?
Answer: Constituent particles are the basic tiny units that make up a larger piece of a substance.
3. Is grinding chalk a physical or chemical change?
Answer: Grinding chalk is a physical change.
4. Why is grinding chalk a physical change?
Answer: Because no new substance is formed; only the size of chalk particles decreases.
5. Can constituent particles be seen with an ordinary microscope?
Answer: No, they are extremely small and cannot be seen with an ordinary microscope.
6. Where does sugar go when it dissolves in water?
Answer: Sugar breaks into tiny particles and occupies spaces between water particles.
7. What are interparticle spaces?
Answer: The spaces between particles of matter are called interparticle spaces.
8. What are interparticle attractions?
Answer: Attractive forces between particles of matter are called interparticle attractions.
9. Who gave the ancient Indian idea of Parmanu?
Answer: Acharya Kanad gave the idea of Parmanu.
10. Which state of matter has definite shape and volume?
Answer: Solid state has definite shape and definite volume.
11. Which state of matter has definite volume but no fixed shape?
Answer: Liquid state has definite volume but no fixed shape.
12. Which state of matter has no fixed shape and no fixed volume?
Answer: Gaseous state has no fixed shape and no fixed volume.
13. What is melting?
Answer: Melting is the conversion of a solid into a liquid on heating.
14. What is melting point?
Answer: Melting point is the minimum temperature at which a solid melts into a liquid at atmospheric pressure.
15. What is the melting point of ice?
Answer: The melting point of ice is 0 °C.
16. What is the melting point of urea?
Answer: The melting point of urea is 133 °C.
17. What is the melting point of iron?
Answer: The melting point of iron is 1538 °C.
18. What is boiling point?
Answer: Boiling point is the temperature at which a liquid boils and turns into vapour at atmospheric pressure.
19. What is evaporation?
Answer: Evaporation is the slow formation of vapour from the surface of a liquid at temperatures below boiling point.
20. Which states of matter are called fluids?
Answer: Liquids and gases are called fluids.
21. Which state has maximum interparticle spacing?
Answer: Gases have maximum interparticle spacing.
22. Which state has strongest interparticle attraction?
Answer: Solids have the strongest interparticle attraction.
23. Which state has negligible interparticle attraction?
Answer: Gases have negligible interparticle attraction.
24. What happens to particle movement when heat is provided?
Answer: Particle movement increases when heat is provided.
Short Answer Questions
1. How does the chalk activity show that matter is particulate?
Answer: A chalk stick can be broken into smaller pieces and then ground into fine powder. Each tiny speck is still chalk. This shows that a larger piece of matter is made of many smaller particles.
2. Why does sugar become invisible after dissolving in water?
Answer: Sugar breaks into extremely small constituent particles. These particles spread and occupy spaces between water particles, so sugar is not visible but can be tasted.
3. What are interparticle spaces? Give an example.
Answer: Interparticle spaces are spaces between particles of matter. When sugar dissolves in water, sugar particles occupy the spaces between water particles.
4. What are interparticle attractions?
Answer: Interparticle attractions are attractive forces that hold particles of matter together. Their strength depends on the nature of the substance and the distance between particles.
5. Why do solids have fixed shape and volume?
Answer: In solids, particles are tightly packed and held by strong interparticle attractions. They can only vibrate about fixed positions and cannot move freely.
6. What happens to particles of a solid on heating?
Answer: On heating, particles of a solid vibrate more vigorously. At the melting point, they overcome some attractive forces and start moving away from fixed positions, changing the solid into a liquid.
7. Why do liquids take the shape of their container?
Answer: Liquid particles can move freely within a limited space. Therefore, liquids do not have a fixed shape and take the shape of the container.
8. Why do liquids have definite volume?
Answer: Liquid particles are still close enough due to interparticle attractions. They can move but remain within a limited space, so liquids have definite volume.
9. Why do gases not have fixed shape or volume?
Answer: Gas particles have maximum interparticle spacing and negligible attraction. They move freely in all directions and fill all available space.
10. Why is air compressible but water practically incompressible?
Answer: Air has large spaces between its particles, so it can be compressed. Water particles have much less space between them, so water is practically incompressible.
11. Why does potassium permanganate spread in water?
Answer: Water particles are in constant motion. They pull out potassium permanganate particles and hit them, spreading them throughout the water.
12. Why does potassium permanganate spread faster in hot water?
Answer: Particles move faster in hot water because heat increases particle movement. Therefore, potassium permanganate spreads fastest in hot water.
13. Why can we smell an incense stick from a distance?
Answer: Fragrance particles spread through air because air particles are constantly moving and hit the fragrance particles, helping them spread throughout the room.
14. Why does sand not dissolve in water like sugar?
Answer: Sand is insoluble in water. Its particles do not separate and occupy spaces between water particles like sugar. Instead, sand settles down and increases the total volume.
15. How does soap help remove oil stains?
Answer: Soap particles surround oil particles. One end of the soap particle attaches to oil and the other mixes with water, helping lift oil from the fabric and wash it away.
Long Answer Questions
1. Explain the particulate nature of matter using chalk and sugar activities.
Answer:
- When chalk is broken and ground, it forms fine powder. Each tiny speck remains chalk, showing that chalk is made of smaller particles.
- If the chalk could be broken further and further, we would reach basic tiny units called constituent particles.
- When sugar dissolves in water, visible sugar grains disappear, but the solution tastes sweet.
- This shows that sugar breaks into tiny particles that spread between water particles.
- Both activities prove that matter is made up of extremely small particles.
2. Explain interparticle spaces with the sugar-water activity.
Answer: When sugar is added to water, the level of water initially increases. After stirring, sugar dissolves and the water level may decrease slightly. This happens because dissolved sugar particles occupy the spaces between water particles. This proves that particles of matter have interparticle spaces between them.
3. Explain interparticle attractions and their role in states of matter.
Answer: Interparticle attractions are attractive forces between particles of matter. In solids, these attractions are strongest, so particles are tightly packed and fixed in position. In liquids, attractions are weaker, so particles can move within limited space. In gases, attractions are negligible, so particles move freely in all directions. Thus, interparticle attractions decide the physical state of matter.
4. Describe the particle arrangement in solids.
Answer: In solids, particles are closely packed with minimum interparticle space. The interparticle attractions are very strong. Particles cannot move freely from one place to another; they only vibrate about their fixed positions. Therefore, solids have a definite shape and a definite volume.
5. Describe the particle arrangement in liquids.
Answer: In liquids, particles are slightly farther apart than in solids. The interparticle attractions are weaker than in solids but still strong enough to keep particles close. Liquid particles can move within limited space. Therefore, liquids have definite volume but no fixed shape and take the shape of their container.
6. Describe the particle arrangement in gases.
Answer: In gases, particles are far apart and have maximum interparticle space. The interparticle attractions are negligible. Gas particles move freely in all directions and occupy all available space. Therefore, gases have no fixed shape and no fixed volume.
7. Differentiate between solids, liquids, and gases on the basis of particles.
| Property | Solid | Liquid | Gas |
|---|---|---|---|
| Interparticle spacing | Minimum | More than solids | Maximum |
| Interparticle attraction | Strongest | Weaker than solids | Negligible |
| Movement of particles | Only vibrations | Restricted movement | Free movement |
| Shape | Fixed | No fixed shape | No fixed shape |
| Volume | Fixed | Fixed | No fixed volume |
8. Explain melting and boiling using particle theory.
Answer: On heating a solid, its particles vibrate more vigorously. At the melting point, particles gain enough energy to move away from their fixed positions, and the solid changes into a liquid. On further heating, liquid particles move faster. At the boiling point, particles gain enough energy to escape from the liquid throughout the liquid, forming vapour or gas.
9. Explain the difference between boiling and evaporation.
Answer: Boiling occurs at the boiling point and vapour formation takes place rapidly throughout the liquid, seen as bubbles. Evaporation occurs at all temperatures below boiling point, but slowly and only at the surface of the liquid. Both involve conversion of liquid into vapour.
10. How does heat affect the movement of particles?
Answer: Heat increases the thermal energy of particles. In hot water, particles move faster than in water at room temperature or ice-cold water. Due to faster particle movement, potassium permanganate spreads fastest in hot water, slower in room-temperature water, and slowest in ice-cold water.
Case-Study Based Questions
Case Study 1: Chalk Powder
A student breaks a chalk stick into smaller pieces and grinds it into fine powder. Even the tiny powder particles are still chalk.
Q1. Is grinding chalk a physical or chemical change?
Answer: It is a physical change.
Q2. Why is no new substance formed?
Answer: Only the size of chalk particles decreases; the substance remains chalk.
Q3. What idea does this activity support?
Answer: It supports the idea that matter is made up of smaller particles.
Case Study 2: Sugar Dissolving in Water
Two teaspoons of sugar are added to water and stirred. The sugar disappears, but the water tastes sweet.
Q1. Where did the sugar go?
Answer: Sugar broke into tiny particles and spread between water particles.
Q2. What does this prove about water?
Answer: It proves that water particles have spaces between them.
Q3. Why can sugar still be detected?
Answer: Its presence can be sensed by taste, even though it is not visible.
Case Study 3: Water in Different Containers
200 mL of water is transferred from one container to another container of different shape. The water takes the shape of each container but its volume remains 200 mL.
Q1. What does this show about liquids?
Answer: Liquids have no fixed shape but have definite volume.
Q2. Why does water take the container’s shape?
Answer: Water particles can move freely within limited space.
Q3. Are liquids fluids?
Answer: Yes, liquids are fluids because they can flow.
Case Study 4: Smoke in Gas Jars
Smoke collected in one gas jar spreads into another empty gas jar when the glass plate between them is removed.
Q1. What does this show about gases?
Answer: Gases have no fixed volume and fill all available space.
Q2. Why does smoke spread?
Answer: Gas particles move freely in all directions and help smoke particles spread.
Q3. What is interparticle attraction like in gases?
Answer: It is negligible.
Case Study 5: Potassium Permanganate in Water
A few grains of potassium permanganate are added to water. Pink streaks spread and later the whole water becomes uniformly pink.
Q1. Why does the colour spread?
Answer: Water particles are in constant motion and spread potassium permanganate particles throughout the liquid.
Q2. What happens in hot water?
Answer: The colour spreads faster because particles move faster in hot water.
Q3. What conclusion can be drawn?
Answer: Particles of matter are always moving, and their movement increases on heating.
Assertion-Reason Questions
Choose the correct option:
A. Both Assertion and Reason are true and Reason is the correct explanation.
B. Both Assertion and Reason are true but Reason is not the correct explanation.
C. Assertion is true but Reason is false.
D. Assertion is false but Reason is true.
1. Assertion: Matter is made up of extremely small particles. Reason: Sugar dissolves in water and spreads as tiny particles between water particles.
Answer: A
2. Assertion: Grinding chalk is a chemical change. Reason: A new substance is formed during grinding.
Answer: D
3. Assertion: Solids have fixed shape and volume. Reason: Particles in solids are tightly packed and strongly attracted.
Answer: A
4. Assertion: Liquids take the shape of their container. Reason: Liquid particles can move within limited space.
Answer: A
5. Assertion: Gases fill all available space. Reason: Gas particles have negligible attraction and move freely in all directions.
Answer: A
6. Assertion: Gases are easily compressible. Reason: Gas particles have large spaces between them.
Answer: A
7. Assertion: Water is practically incompressible. Reason: Water particles have very large spaces between them.
Answer: C
8. Assertion: Heating increases the movement of particles. Reason: Potassium permanganate spreads faster in hot water.
Answer: A
9. Assertion: Liquids and gases are called fluids. Reason: Both liquids and gases can flow.
Answer: A
10. Assertion: Evaporation occurs only at boiling point. Reason: Vapour formation can occur below boiling point from the surface of a liquid.
Answer: D
Competency-Based and Critical Thinking / HOTS Questions
1. If all constituent particles are removed from a chair, what will remain?
Answer: Nothing of the chair will remain because the chair itself is made up of constituent particles.
2. Why do gases mix easily, while solids do not?
Answer: Gas particles move freely in all directions and have maximum interparticle space. Solid particles are fixed in position due to strong attractions, so solids do not mix easily.
3. Milk spreads on a table, but the glass tumbler keeps its shape. Why?
Answer: Milk is a liquid, so it flows and has no fixed shape. The glass tumbler is a solid, so it has fixed shape due to tightly packed particles.
4. Why does ocean water taste salty even though salt is not visible?
Answer: Salt dissolves in water and breaks into tiny particles that spread between water particles. It is not visible but can be detected by taste.
5. Rice grains take the shape of a jar. Are they liquids?
Answer: No, rice grains are solids. Each grain has a fixed shape and volume. The collection appears to take the container’s shape because grains can move over one another.
6. Why does perfume fragrance spread throughout a room?
Answer: Fragrance particles mix with air particles. Since gas particles move freely in all directions, the smell spreads throughout the room.
7. Why does an inflated balloon become bigger when kept in hot water?
Answer: Heating increases the motion of air particles inside the balloon. They move faster and push the balloon outward, increasing its size.
8. Why does sand settle at the bottom of water?
Answer: Sand is insoluble in water. Its particles do not separate and occupy spaces between water particles, so they settle at the bottom.
9. Why does iodine vapour spread inside a gas jar?
Answer: Vapour particles move freely in all directions and occupy the entire available space of the gas jar.
10. How does thermal energy decide the physical state of matter?
Answer: When thermal energy is low, particles remain close and form solids. With more energy, particles move more and form liquids. With enough energy to overcome attractions, particles move freely and form gases.
Diagram-Based Questions
Diagram 1: Particles in Three States of Matter
Solid
Liquid
Gas
Question: Which state has maximum interparticle spacing?
Answer: Gaseous state has maximum interparticle spacing.
Diagram 2: Sugar Dissolving in Water
Question: Why does the solution taste sweet even when sugar is not visible?
Answer: Sugar particles are present between water particles, but they are too small to see.
Diagram 3: Heating a Solid
Question: What happens to solid particles on heating?
Answer: They vibrate more vigorously and may leave fixed positions at the melting point.
Diagram 4: Compressing Air in a Syringe
Question: Why can air be compressed?
Answer: Air has large spaces between particles that can be reduced by pressure.
Diagram 5: Fragrance Spreading
Question: What does spreading of fragrance prove?
Answer: It proves that gas particles are constantly moving.
Quick Revision Box
- Matter is made up of extremely small particles.
- Constituent particles are the basic units of a substance.
- Grinding chalk is a physical change.
- Sugar dissolves by occupying spaces between water particles.
- Particles of matter have interparticle spaces.
- Particles are held by interparticle attractions.
- Solids have fixed shape and fixed volume.
- Liquids have fixed volume but no fixed shape.
- Gases have no fixed shape and no fixed volume.
- Solids have strongest interparticle attraction.
- Gases have maximum interparticle spacing.
- Liquids and gases are fluids because they can flow.
- Heating increases movement of particles.
- Melting is solid to liquid change.
- Boiling is rapid vapour formation throughout a liquid.
- Evaporation is slow vapour formation from the surface.
Important Exam Tips
Interactive Quiz
Choose the correct answer and click submit.
Frequently Asked Questions
1. What is the particulate nature of matter?
It means matter is made up of extremely small constituent particles.
2. What are constituent particles?
Constituent particles are the tiny basic units that make up a substance or material.
3. Why does sugar disappear in water?
Sugar breaks into tiny particles and occupies spaces between water particles.
4. What are interparticle spaces?
Interparticle spaces are the empty spaces between particles of matter.
5. What are interparticle attractions?
They are attractive forces that hold particles of matter together.
6. Why do solids have fixed shape?
Solids have fixed shape because their particles are tightly packed and strongly attracted.
7. Why do liquids flow?
Liquids flow because their particles can move within limited space.
8. Why do gases fill the entire container?
Gas particles move freely in all directions and have negligible attraction, so they fill all available space.
9. What is the difference between boiling and evaporation?
Boiling occurs throughout the liquid at boiling point, while evaporation occurs slowly at the surface at all temperatures.
10. Why does smell spread in air?
Smell spreads because fragrance particles mix with moving air particles and spread throughout the available space.
Final Conclusion
The chapter Particulate Nature of Matter explains that all matter is made of extremely small particles. These particles have spaces between them, attract one another, and remain in motion. Differences in particle spacing, attraction, and movement explain the properties of solids, liquids, and gases. Heating increases particle motion and can change one state of matter into another.
Leave a Reply