Class 8 Science · Original EZT practice
Particulate Nature of Matter (Class 8 Science Chapter 7): everything is made of moving particles
Sugar vanishes in water, a smell crosses the room, a balloon swells with air - none of it is magic. Matter is made of tiny particles in constant motion, and that one idea explains all three states of matter. Below: the ideas in plain words, then original EZT practice with worked answers. (Note: this is original practice, not a textbook exercise key.)
10 original worked examples, 10 fresh self-check questions, with explained answers. These are not copied textbook exercises, an official chapter index or a full answer key. No affiliation with NCERT is claimed.
Official sources for topic and edition context, checked 17 October 2026:
1. Matter is made of particles
Everything that occupies space and has mass is matter - and all matter is built from tiny particles far too small to see. Dissolving is the first clue: the sugar does not disappear, its particles just spread among the water particles.
2. Particles are always moving
The particles of matter never sit still. This motion is why smells travel: scent particles leave the source, move through the air and reach your nose - a spreading called diffusion.
3. The three states: arrangement and attraction
In solids, particles are tightly packed and attract strongly - so a solid keeps its own shape. In liquids, particles are close but can slide past each other - a liquid takes the shape of its container but keeps its volume. In gases, particles are far apart and move freely - a gas fills the whole container.
4. Evaporation and cooling
In a liquid, the faster surface particles escape into the air - evaporation. It happens at all temperatures, speeds up with heat, wind and larger surface area, and takes energy away, leaving the remaining liquid cooler.
Choose, solve, check, then try a fresh question.
Before calculating, read the method prompt and name the condition that makes it useful. Write your own attempt. Open the steps only when you need them, and use the check to catch a wrong sign, unit or interpretation. Finish with the fresh question before reading its answer.
Explain sugar dissolving without a level rise
Choose the method: Use the spaces between water particles.
EZT practice question
A spoon of sugar dissolves in a glass of water without the water level rising much. Explain.
Show the worked solution
- Water particles have spaces between them.
- Sugar particles separate and occupy many of those spaces.
Answer: There are spaces between the water particles, and the sugar particles settle into those spaces.
Check: The sugar is still present even though the level barely changes.
Watch for this: Dissolved sugar has not vanished or become weightless.
Now try it yourself
Why can a little salt dissolve in a full cup of water without overflowing it?
Check your answer
Salt particles fit into spaces between water particles.
Particles are not packed with every gap filled.
Explain sweetness spreading through water
Choose the method: Follow where the sugar particles go after dissolving.
EZT practice question
The water now tastes sweet throughout, even without stirring the bottom. Why?
Show the worked solution
- Sugar particles spread among the water particles.
- Over time they become evenly distributed.
Answer: The sugar particles have spread evenly among the water particles - the sugar is still present, just invisibly mixed.
Check: Sweetness in every sip shows the particles are distributed through the liquid.
Watch for this: Sweet water is a mixture; the sugar has not chemically disappeared.
Now try it yourself
Why does a drop of honey eventually make a whole glass taste sweet?
Check your answer
Honey particles spread among the water particles.
Dissolved particles move and mix through the liquid.
Connect a travelling smell with particle motion
Choose the method: Name diffusion, then connect it to moving scent particles.
EZT practice question
Food cooking in the kitchen can be smelled in the next room. Which property of particles explains this?
Show the worked solution
- Scent particles leave the hot food.
- They move through the air and spread into the next room.
Answer: Particles of the aroma are constantly moving and diffuse through the air.
Check: The smell travels without anyone carrying the food into the next room.
Watch for this: The air does not need a fan for diffusion to happen; a fan only speeds the mixing.
Now try it yourself
Why can perfume sprayed near a door be smelled across the room?
Check your answer
Perfume particles move and diffuse through the air.
Their constant motion carries them away from the source.
Explain ink spreading in still water
Choose the method: Check that mixing happens without stirring.
EZT practice question
A drop of ink placed in still water slowly colours all of it. What does this show?
Show the worked solution
- The water is not stirred.
- Ink particles and water particles move and mix on their own.
Answer: The ink particles and water particles are moving and mix on their own - diffusion needs no stirring.
Check: The slow colour spread is evidence for particle motion.
Watch for this: The colour spreading is not caused by the ink disappearing; it is becoming more spread out.
Now try it yourself
Why does a drop of food colour eventually colour a whole bowl of still water?
Check your answer
Its particles diffuse through the water.
Both sets of particles are always moving.
Compare diffusion from hot and cold food
Choose the method: Use temperature to compare particle speed.
EZT practice question
Why does the smell of hot food reach you faster than the smell of cold food?
Show the worked solution
- Higher temperature gives particles more energy.
- Faster aroma particles spread through the air more quickly.
Answer: Particles move faster at higher temperature, so the aroma diffuses more quickly.
Check: The same food smell is stronger sooner when the food is hot.
Watch for this: Cold food still gives off particles; they just move and spread more slowly.
Now try it yourself
Why does hot tea often smell stronger than cold tea?
Check your answer
Aroma particles leave and spread faster from hot tea.
Higher temperature increases particle motion.
Contrast a solid and a liquid by particle arrangement
Choose the method: Compare fixed particles with particles that slide.
EZT practice question
Why does a stone keep its shape but water does not?
Show the worked solution
- Stone is a solid with particles held tightly in fixed positions.
- Water is a liquid with particles that can slide past one another.
Answer: In the stone (solid) the particles are held tightly in fixed positions; in water (liquid) they can slide over one another, so the water takes the container's shape.
Check: The solid keeps its own shape, while the liquid matches its container.
Watch for this: A liquid changes shape without changing into a gas; its particles remain close.
Now try it yourself
Why does milk poured from a jug into a bowl take the bowl's shape?
Check your answer
Milk particles can slide past one another.
A liquid has no fixed shape of its own.
Explain why gases compress more easily
Choose the method: Compare the space between particles in each state.
EZT practice question
Why can a gas be compressed easily but a solid cannot?
Show the worked solution
- Gas particles are far apart.
- Solid particles are already packed tightly together.
Answer: Gas particles have large spaces between them that squeezing can close; solid particles are already packed tight, leaving no room.
Check: Compression reduces the empty space, not the particles themselves.
Watch for this: Do not say gas particles shrink; the spaces between them get smaller.
Now try it yourself
Why can air in a syringe be pushed into a smaller volume?
Check your answer
The spaces between air particles can be reduced.
Gas particles are far apart before compression.
Use moving particles to explain a firm balloon
Choose the method: Connect particle collisions with pressure on the balloon wall.
EZT practice question
An inflated balloon stays firm. Explain using particles.
Show the worked solution
- Air particles inside the balloon keep moving.
- They collide with the inside wall and push it outward.
Answer: Air particles inside keep moving and pushing against the balloon's walls, holding it stretched.
Check: The outward pushes balance the balloon material pulling inward.
Watch for this: The balloon is not firm because the air is still; moving particles create the pushes.
Now try it yourself
Why does a balloon become softer after some air escapes?
Check your answer
Fewer air particles remain to push on its walls.
Fewer collisions produce less outward push.
Compare evaporation from a plate and a bottle
Choose the method: Look at how much liquid surface is open to the air.
EZT practice question
Why does water in an open plate dry faster than water in a bottle?
Show the worked solution
- Evaporation happens from the liquid surface.
- A plate exposes a much larger surface than a bottle mouth.
Answer: The plate offers a much larger surface, so far more particles are at the surface and can escape.
Check: More exposed surface means more chances for particles to leave.
Watch for this: The water in the plate is not hotter just because it is spread out.
Now try it yourself
Why does a thin puddle dry faster than a deep small puddle?
Check your answer
The thin puddle has a larger exposed surface for its water particles to escape from.
Evaporation is fastest where liquid meets air.
Explain cooling from quick evaporation
Choose the method: Track where the energy for evaporation comes from.
EZT practice question
Why do you feel cool when spirit (or aftershave) is rubbed on your skin?
Show the worked solution
- Spirit evaporates quickly from the skin.
- The energy needed for evaporation is taken from the skin.
Answer: It evaporates quickly, and the energy needed for evaporation is drawn from your skin - cooling it.
Check: Losing energy makes the skin feel cooler.
Watch for this: The spirit is not cold by itself; evaporation removes energy from the skin.
Now try it yourself
Why does a wet hand feel cooler in moving air?
Check your answer
Moving air speeds evaporation, which removes energy from the skin faster.
Faster evaporation takes energy away faster.
Try it yourself
Work these on paper before checking any notes. Answers are deliberately not shown here.
- Camphor left in the open slowly disappears - explain with particles.
- Why does the smell of incense spread through the whole house?
- Arrange solid, liquid and gas in order of the spaces between their particles.
- Why do wet clothes dry faster on a windy day?
Know the rule but lose track of the steps?
Bring your book edition, your school topic list and a question you attempted. Ask a tutor to explain the choice of method and test it with a different problem. Agree the lesson topics, schedule and fee before starting.
For cost context, see home tuition fees in Delhi NCR. Agree the topics, schedule and fee with your chosen tutor.
Questions about this practice page
- What is matter made of?
- Tiny particles - too small to see - that have spaces between them, attract each other and are always moving.
- What is diffusion?
- The spreading of particles of one substance through another on their own, like a smell moving through air or ink colouring still water.
- Why do solids, liquids and gases behave differently?
- The packing and attraction of their particles differ - tight and fixed in solids, close but sliding in liquids, far apart and free in gases.
- Why does evaporation cause cooling?
- The escaping particles carry energy away with them, drawing it from the surface they leave - so the skin or liquid left behind cools.
- Are these the NCERT exercise questions for Particulate Nature of Matter?
- No. EZT pages are original practice on this chapter - use them to prepare for the textbook exercises, not as a substitute for your book.