Class 8 Science Chapter 7: Particulate Nature of Matter Solutions

NCERT Solutions for Class 8 Science Chapter 7: Particulate Nature of Matter (2025-26)

1. Multiple choice questions.

1. The primary difference between solids and liquids is that the constituent particles are:

• (a) closely packed in solids, while stationary in liquids
• (b) far apart in solids, fixed position in liquids
• (c) always moving in solids, fixed position in liquids
• (d) closely packed in solids and move past each other in liquids

Answer: (d) closely packed in solids and move past each other in liquids.

2. Answer the following questions in about 30 words.

1. Melting ice is transformation of solid to liquid. Is this statement true or false? Give reason.

Answer: True. Melting ice is the transformation of water from its solid state (ice) to its liquid state due to increase in temperature, which causes the particles to move more freely.

2. Why does ocean water taste salty, even though salt is not visible?

Answer: Ocean water tastes salty because salt is dissolved in the water at the particle level. The salt particles mix with water particles, becoming invisible to the naked eye but still present and providing the salty taste.

3. Why do gases mix easily, while solids do not?

Answer: Gases mix easily because their particles are far apart and move freely in all directions. In solids, particles are tightly packed and can only vibrate, making it difficult for them to mix with each other.

4. Grains of rice and rice flour take the shape of a container. Are they solids or liquids? Explain.

Answer: Both grains of rice and rice flour are solids. Each grain or flour particle has a fixed shape, but as a collection, they can flow and take the shape of a container due to the spaces between the grains or particles.

3. Answer the following questions in about 150 words.

1. Draw a diagram showing the arrangement of particles as ice melts and becomes water vapour. Explain the changes in terms of particle behavior.

Answer: (Diagram to be drawn by student as per textbook guidance.)
When ice (solid) is heated, its particles gain energy and start vibrating more quickly. At the melting point, the attractions between particles weaken and they move out of their fixed positions, becoming liquid water. Upon further heating, particles in water gain enough energy to completely overcome attractions, moving freely as water vapour (gas). Thus, from solid to liquid to gas, particles move from a closely packed fixed arrangement, to a loosely packed mobile state, to being far apart and completely free to move.

2. Justify: Milk flows on the table, tumbler does not.

Answer: Milk is a liquid, whereas a tumbler is a solid. Liquid particles are loosely packed and can move past each other, allowing liquids to flow and take the shape of their container or spread on a surface. Solid particles in a tumbler are tightly packed, have a definite shape, and do not flow, so the tumbler keeps its form and doesn’t spread.

3. Draw pictures to show particle arrangements in:

• Aluminium foil
• Glycerin
• Methane gas

Answer: (Diagrams to be made by student)
Aluminium foil: particles closely packed in regular pattern (solid).
Glycerin: particles are close but not fixed, able to move around (liquid).
Methane gas: particles are far apart and spread randomly throughout the container (gas).

4. Observe Fig. 7.16a (candle just extinguished). Identify states of wax, match to Fig. 7.16b (particle arrangement).

Answer: In Fig. 7.16a, after extinguishing the candle, wax near the flame is in the gaseous state (vapor), the molten wax is in the liquid state, and the part of the candle still unchanged is solid wax. In Fig. 7.16b, the particle arrangements correspond as: (a) closely packed (solid), (b) loosely packed (liquid), (c) free and far apart (gas).

4. Match the following.

Question	Answer
1. Melting point	(B) Minimum temperature at which a solid melts
2. Fluid	(C) Flows easily (liquid or gas)
3. Interparticle space	(A) Empty space between particles
4. Boiling point	(D) Temperature at which a liquid becomes gas rapidly

5. Choose correct answer. If all constituent particles are removed from a chair, what remains?

• (a) Nothing will change
• (b) Chair will weigh less
• (c) Nothing of the chair will remain

Answer: (c) Nothing of the chair will remain.

6. Which statements are true? Correct the false ones.

1. Melting ice is transformation of solid to liquid.
2. Melting decreases interparticle attractions.
3. Solids have fixed shape and volume.
4. Interactions in solids are strong, spaces are small.

Answer:
1. True.
2. True.
3. True.
4. True.

Particulate Nature of Matter – Key Concepts & Exam Tips (Class 8, 2025-26)

Understanding the particulate nature of matter is essential for mastering Class 8 Science. These concepts explain how solids, liquids, and gases differ in particle arrangement, movement, and behavior, making them crucial for strong exam preparation.

Learning about interparticle spaces and forces helps you answer application-based questions easily. Regular revision and drawing diagrams will boost your confidence and help you retain information effectively for the 2025-26 exam season.

Practice exercise-based NCERT questions and focus on keywords such as melting point, boiling point, and particles' movement. These strategies can help you score higher and understand the core ideas of Class 8 Science Chapter 7.