Particulate Nature of Matter

Correct Option: (iv) closely packed in solids and move past each other in liquids.

Justification:
In solids, the constituent particles are tightly packed and held in fixed positions by very strong interparticle forces of attraction; they can only vibrate about their mean positions but cannot move past each other.

In liquids, the particles are still relatively close together but the interparticle forces are slightly weaker, allowing the particles to move past each other freely within a limited space. This is why liquids flow and take the shape of their container.

Options (i), (ii), and (iii) are incorrect because:
- Particles in liquids are NOT stationary — they move freely.
- Particles in solids are NOT far apart — they are closely packed.
- Particles in solids do NOT always move freely — they only vibrate about fixed positions.

(i) TRUE.
Melting ice into water is indeed an example of transformation of a solid (ice) into a liquid (water). When ice is heated to its melting point (0°C), it absorbs heat energy and changes into liquid water.

(ii) TRUE.
During melting, heat energy is supplied to the solid. This energy weakens the strong interparticle forces of attraction, allowing particles to move more freely. Hence, interparticle attractions decrease during the melting process.

(iii) TRUE.
Solids have a fixed (definite) shape and a fixed (definite) volume. This is because the particles in solids are tightly packed and held in fixed positions by strong interparticle forces, preventing them from moving freely.

(iv) TRUE.
In solids, the interparticle forces of attraction are very strong, and the particles are closely packed, leaving very little (minimum) interparticle space between them.

(v) TRUE.
When camphor is heated, it sublimes (converts directly from solid to vapour/gas). The gaseous particles of camphor move freely in all directions and spread throughout the room, so the fragrance reaches all corners.

(vi) FALSE.
Corrected statement: On heating camphor, we are adding energy to it, which causes it to sublime (convert into vapour). The camphor vapour (gas particles) then diffuses and spreads throughout the room. The fragrance we smell is due to the camphor vapour particles reaching our nose — the energy is NOT released as a smell. The smell is caused by the movement and diffusion of camphor vapour particles.

Correct Option: (iii) Nothing of the chair will remain.

Justification:
All matter is made up of constituent particles (atoms and molecules). The chair — whether made of wood, metal, or plastic — is entirely composed of these constituent particles. If all the constituent particles were removed, there would be nothing left of the chair. The chair exists only because of the collective arrangement of its constituent particles. Hence, removing all particles means the chair ceases to exist entirely.

Option (i) is incorrect because the chair is made entirely of particles, so removing them changes everything.
Option (ii) is incorrect because the chair would not merely weigh less — it would not exist at all.

Given: We need to explain why gases mix easily but solids do not.

Concept Used: Interparticle spacing and freedom of movement of particles in different states of matter.

Explanation:

Gases mix easily because:
- The interparticle forces of attraction in gases are negligible (almost zero).
- The particles of gases are very far apart from each other, resulting in maximum interparticle spacing.
- Gas particles are completely free to move in all directions with high speed.
- When two gases are placed together, their particles intermingle freely and spread throughout the available space. This process is called diffusion.
- Example: When an incense stick is lit in one corner of a room, its fragrance (vapour particles) spreads to all corners due to free movement of gas particles.

Solids do not mix easily because:
- The interparticle forces of attraction in solids are very strong.
- The particles are tightly packed with minimum interparticle spacing.
- The particles of solids are held in fixed positions and can only vibrate about their mean positions — they cannot move freely from one place to another.
- Therefore, the particles of one solid cannot intermingle with the particles of another solid easily.

Conclusion: The negligible interparticle attraction and maximum interparticle spacing in gases allow their particles to move freely and mix easily, whereas the strong interparticle attraction and minimum interparticle spacing in solids prevent their particles from moving and mixing.

Given: Milk (liquid) flows and spreads when spilled; glass tumbler (solid) retains its shape.

Concept Used: Properties of solids and liquids based on interparticle forces and particle movement.

Justification:

Why milk flows and spreads out (Liquid behaviour):
- Milk is a liquid. In liquids, the interparticle forces of attraction are slightly weaker than in solids.
- The particles of milk are free to move past each other within a limited space.
- Because the particles can move freely, milk does not have a fixed shape.
- When spilled, the milk particles flow under gravity and spread out, taking the shape of the surface (the table) on which they are placed.
- Liquids and gases are called fluids because they can flow.

Why the glass tumbler retains its shape (Solid behaviour):
- The glass tumbler is a solid. In solids, the interparticle forces of attraction are very strong.
- The particles are tightly packed and held in fixed positions; they can only vibrate about their mean positions but cannot move past each other.
- Because the particles cannot move freely, the solid maintains a definite, fixed shape and volume.
- Therefore, even when the tumbler falls, it retains its original shape (unless it breaks due to impact).

Conclusion: The difference in behaviour is due to the difference in interparticle forces and freedom of movement of particles — weaker forces and free movement in liquids (milk) allow it to flow and spread, while strong forces and fixed positions in solids (glass tumbler) allow it to retain its shape.