NCERT Solutions Class 8 Science Chapter 7 2026-27 PDF

The correct option is (iv): closely packed in solids and move past each other in liquids. Concept used. Solids and liquids both have particles fairly close together, but their freedom of movement is different. Solid particles mainly vibrate about fixed positions, while liquid particles can move past one another within a limited space.

1. In a solid, interparticle attractions are strong. The particles stay in fixed positions and only vibrate.
2. In a liquid, interparticle attractions are weaker than in a solid. The particles remain close but can slide past each other.
3. Option (i) is wrong because solid particles are not completely stationary. They vibrate.
4. Option (ii) is wrong because solid particles are not far apart.
5. Option (iii) is wrong because liquid particles, not solid particles, move past one another.

Statements (i), (ii), (iii), (iv) and (v) are true. Statement (vi) is false. Concept used. A true-false answer should test each statement against particle arrangement, attraction and movement. Melting weakens effective attraction enough for particles to leave fixed positions. Smell travels because vapour particles spread through air.

1. Statement (i) is true. Ice is a solid and water is a liquid.
2. Statement (ii) is true. During melting, particles gain energy and leave fixed positions, so attraction is effectively overcome.
3. Statement (iii) is true. A solid has a definite shape and a definite volume.
4. Statement (iv) is true. Solid particles are strongly held with very small spaces between them.
5. Statement (v) is true. Heated camphor forms vapour, and vapour particles spread through air.
6. Statement (vi) is false. Energy is not released as smell. Heating gives energy to camphor particles, and camphor vapour carries the smell.

The correct option is (iii): nothing of the chair will remain. Concept used. Matter is made up of constituent particles. The shape, mass and volume of any object come from its particles and from how those particles are arranged.

1. A chair is matter. It has mass and occupies space.
2. The chair's wood, plastic or metal is made of constituent particles.
3. If every constituent particle is removed, no material is left.
4. Without material particles, there is no mass, volume or structure.
5. So the chair cannot keep any shape at all.

Gases mix easily because their particles move freely with large spaces between them. Solids do not mix by themselves because their particles are fixed in position. Concept used. Diffusion is the spreading and mixing of particles. Gas particles have large spaces, negligible attractions and free motion in all directions. Solid particles are closely packed and held in fixed positions.

1. In gases, particles are far apart from one another.
2. The interparticle attractions in gases are negligible.
3. Gas particles move freely in all available space and collide with particles of other gases.
4. This free motion helps one gas spread into another gas easily.
5. In solids, particles are closely packed and held by strong attractions.
6. Solid particles cannot move from place to place, so two solids do not mix on their own like gases.

Milk flows because its particles can move past each other. The glass tumbler keeps its shape because its particles are strongly held in fixed positions. Concept used. Milk is a liquid, and a tumbler is a solid. A liquid has a definite volume but no fixed shape. A solid has a fixed shape and a fixed volume.

1. Milk is a liquid. Its particles are close together but can move within a limited space.
2. Because of this movement, milk has no fixed shape and can spread over the table.
3. The glass tumbler is a solid. Its particles are closely packed.
4. Strong interparticle attractions hold the glass particles in fixed positions.
5. So the tumbler has a fixed shape even when milk is poured out or spilled.

Draw three boxes: ice with tightly packed particles, water with close but irregular particles, and water vapour with far apart particles. Concept used. When ice melts and then changes into water vapour, particle spacing and movement increase. Ice has tightly packed particles, liquid water has close but mobile particles, and water vapour has far apart particles moving freely.

1. In ice, show particles very close together in a regular arrangement.
2. Mark that these particles mainly vibrate about fixed positions.
3. In liquid water, show particles still close but less regular.
4. Mark that liquid particles can move past one another within a limited space.
5. In water vapour, show particles far apart with arrows in different directions.
6. Mark that gas particles move freely through the available space.

Aluminium foil has close fixed particles. Glycerin has close but irregular mobile particles. Methane gas has far apart particles moving freely. Concept used. Aluminium foil is a solid, glycerin is a liquid, and methane is a gas. Their particle pictures should match the particle arrangement in these three states.

1. For aluminium foil, draw many dots packed closely in a regular pattern.
2. For glycerin, draw dots close together but slightly irregular and able to slide.
3. For methane gas, draw dots far apart with arrows showing random motion.
4. Label aluminium foil as solid, glycerin as liquid and methane as gas.
5. Write one property under each drawing: fixed shape for solid, flow for liquid and filling space for gas.

Solid wax matches closely packed particles. Molten wax matches close but mobile particles. Wax vapour matches far apart particles. Concept used. Wax can be present as solid wax, liquid molten wax and wax vapour. These match solid, liquid and gas particle arrangements respectively.

1. The hard body of the candle is solid wax. It matches the tightly packed particle arrangement.
2. The melted wax near the wick is liquid wax. It matches particles that are close but can move past one another.
3. The vapour or smoke near the recently extinguished wick contains wax particles in gaseous form.
4. This vapour matches particles that are far apart and move freely.
5. So the candle can show all three states of wax around the wick after burning.

Ocean water tastes salty because salt particles are dissolved and spread through the water, even though they are too small to see. Concept used. Dissolution spreads very small solute particles between water particles. The dissolved salt particles are too small to see, but they still remain present in water.

1. Salt dissolves in ocean water and separates into extremely small particles.
2. These particles spread throughout the water.
3. They occupy spaces between water particles.
4. The particles are not visible to the eye or an ordinary microscope in this dissolved form.
5. The tongue can still sense the dissolved salt particles by taste.

They are solids. The collection takes the container shape because the grains are small and can rearrange, but each grain remains solid. Concept used. A heap of small solid pieces can pour and settle into a container shape, but each individual grain or flour particle remains a solid with its own shape and volume.

1. A rice grain has its own definite shape and volume.
2. A rice flour particle is also a tiny solid particle.
3. When many such particles are poured into a jar, they rearrange and fill the available space.
4. This makes the heap look like it has taken the jar's shape.
5. However, the individual grains or flour particles do not flow like liquid particles.
6. So rice and rice flour are solids, not liquids.