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Class 8 Science: Particulate Nature of Matter, 8 practice questions with answers

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These are 8 practice questions on Class 8 Science Chapter 7, Particulate Nature of Matter, of the new NCERT textbook, Curiosity. Each has a worked answer and the textbook page it comes from. They cover why broken pieces do not join again, what melting tells you about interparticle attraction, why honey is a liquid, what the bubbles in boiling water are, why wet things dry without boiling, dust and the particles of matter, why a gas fills a bottle but a liquid does not, and why ice is a special case. Try each one before you open the answer.

These questions are our own, drafted with AI help, and every answer was checked against the textbook page it cites, but no practising teacher has reviewed them yet. If you find a mistake, please tell us.

What the chapter says you need

Facts from the NCERT textbook (Curiosity: Textbook of Science for Grade 8, Chapter 7, printed pages 98 to 115):

What matter is made of

Question 1. A pencil lead snaps in two. Kavi presses the two broken ends firmly together, but they do not join again. He says, "The particles in the lead have lost their attraction for good." Find his mistake.

Answer: the attraction depends on distance, and pressing by hand cannot bring the particles close enough again. The particles in each piece still attract each other, which is why each piece stays whole. Interparticle attraction depends on the distance between particles, and even a slight increase in distance decreases it drastically. Pressing the broken ends together by hand cannot bring the particles back as close as they were before the break, so the attraction across the break stays too weak to join the pieces. (Interparticle attractions and distance, page 101.)

Question 2. On a warm day, a piece of chocolate melts in Riya's hand, but a copper coin in her other hand does not melt at all. In which of the two are the interparticle attractions stronger? Explain.

Answer: in the copper coin. A solid melts when its particles vibrate so vigorously that they leave their positions. Solids with weak interparticle attractions have low melting points and melt easily, like the chocolate in a warm hand. Solids with strong attractions have high melting points, so the copper does not melt at that temperature. (Melting and the melting point, pages 102 and 103.)

States of matter

Question 3. Anu says, "Honey is not a liquid, because it flows so slowly." Find her mistake.

Answer: flowing slowly does not stop honey being a liquid. Honey flows and takes the shape of whatever jar or spoon it is in, while its volume stays the same. Having a fixed volume but no fixed shape is what makes something a liquid, and anything that flows is a fluid. How fast it flows does not decide its state. (Liquids, page 104; fluids, page 106.)

Question 4. Neel watches water boiling in a pot and says, "The bubbles rising from the bottom are bubbles of air." Find his mistake.

Answer: the bubbles are water vapour forming inside the boiling water. At the boiling point, the particles move so vigorously that they escape from the liquid and form vapour very fast. This happens not only at the surface but also within the liquid, and we see it as bubbles. So the bubbles in boiling water are bubbles of water vapour. (Boiling, page 105.)

Question 5. Meera says, "Water turns into vapour only when it boils, so my wet hair cannot dry until it gets very hot." Find her mistake.

Answer: water also turns into vapour at lower temperatures, by evaporation. Vapour formation happens at all temperatures, even below the boiling point, but slowly and only at the surface. This slower process is evaporation, and it is how wet hair, wet clothes and spilled water dry at room temperature. (Boiling and evaporation, page 105.)

Question 6. Some water and some air are each moved from a small closed bottle into a large, empty, closed bottle (the water into one large bottle, the air into another). Which of the two now fills its whole large bottle, and why?

Answer: only the air fills the whole bottle; the water keeps its volume. Liquids have a fixed volume but no fixed shape: the water takes the shape of the bottom of the large bottle, but its volume stays the same, so it fills only part of the bottle. The particles of a gas move freely in all directions and their attraction is negligible, so a gas has no fixed volume and fills all the space available to it. (Liquids, page 104; the gaseous state, page 106.)

Spaces between particles

Question 7. In a sunbeam coming through a window, Ravi sees tiny dust specks floating. He says, "These are the constituent particles of air." Find his mistake.

Answer: dust specks are far bigger than the constituent particles of matter. The constituent particles are so small that they cannot be seen even through an ordinary microscope, let alone with the naked eye. The dust in the air, called suspended particulate matter (SPM), is made of tiny dust particles, each of which is itself made up of a very large number of constituent particles. (Constituent particles, page 101; SPM, page 109.)

Question 8. Dev says, "In a solid, the particles are always closer together than in the liquid form of the same substance, so the particles in ice must be closer than in water." Is he right?

Answer: no; ice is an exception. Generally, the particles in a liquid are somewhat farther apart than in its solid. But the book points out that ice is an exception: its particles are farther apart than those in liquid water. So Dev's general rule does not hold for ice and water. (Ice as an exception, page 103.)

Questions students ask

What are interparticle attraction and interparticle space? Interparticle attraction is the force that holds the constituent particles of matter together; interparticle space is the gap between the particles. Both decide the state of a substance. (Pages 101 and 109.)

What is the melting point of a solid? The minimum temperature at which a solid melts to become a liquid at atmospheric pressure. Solids with weak interparticle attractions have low melting points, and those with strong attractions have high ones. (Pages 102 and 103.)

What are fluids? Substances that flow and do not keep a fixed shape: liquids and gases. (Page 106.)

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Sources

All opened and read on 22 October 2026. Page numbers are the printed page numbers of the textbook; printed page = PDF page + 97.

The facts are from the textbook pages above. The questions and worked answers are our own. This guide is general information; follow your teacher and the textbook.