NCERT Solutions Curiosity Chapter 8 and 1518.3 What are the Different States of Water? — In-text Questions
Book page 150 Updated on2026-09-05
Q1.
What are the differences in the properties of water in solid, liquid and gaseous states?
Answer
The three states differ in shape, flow, spreading and volume — and all of these follow from how the tiny particles are arranged.
The same substance in three states. In ice the particles sit in a fixed, regular arrangement and can only vibrate in place. In water they are still close together but can slide past one another. In water vapour they are far apart and move freely, filling all the space available.
The differences, in the words of the chapter:
Ice (solid): retains its shape whatever the container. Does not flow and does not spread.
Water (liquid): flows and changes its shape. It has no fixed shape and takes the shape of the container, but its volume remains constant. It also spreads, again keeping the volume constant.
Water vapour (gas): spreads out in the entire available space. Gases do not possess a fixed shape. Water vapour exists even at room temperature, though it is invisible to us, and it is present in the air around us.
Why the particle picture explains everything: shape is fixed when particles are locked (solid); volume is fixed when particles touch each other, whether locked or sliding (solid and liquid); neither is fixed when particles are far apart and free (gas).
Q2.
Look around and find some examples of solid substances. What are the other examples of liquids you can think of? Think of five more examples. What are the other examples of gases you can think of?
Answer
The book starts you off — solids: stones, wood, glass; liquids: milk, oil; gases: oxygen, carbon dioxide. Here are plenty more from around you.
Solids
Liquids
Gases
Stone, brick, wood
Milk
Oxygen
Glass, steel, copper wire
Mustard or coconut oil
Carbon dioxide
Chalk, pencil, book
Honey
Nitrogen
Ice, sugar, salt
Kerosene and petrol
Water vapour
Plastic ruler, rubber, cloth
Vinegar, lemon juice, tea
LPG (cooking gas)
Candle wax, ghee in winter
Ink, sanitiser, buttermilk
Helium in a balloon; the air itself
Five more liquids, as the book asks: honey, kerosene, lemon juice, ink and buttermilk (chaas).
A caution worth remembering: the same substance can appear in more than one state. Wax, oil and ghee are named in the chapter for exactly this reason — ghee and coconut oil are liquid in summer and solid in winter, and wax is solid in the candle but liquid in the pool near the flame. The state depends on the temperature, not on the name of the substance.
Tip: When you list a gas, remember that most gases are invisible. Do not write "smoke" or "steam" as gases — smoke contains solid particles and steam contains liquid droplets.
Q3.
Have you ever noticed that you can smell the food being cooked even without entering the kitchen? How does this smell reach us?
Answer
Yes. The smell reaches us because it travels through the air, as a gas.
When food is heated, very tiny particles of the smelling substances in it escape from the surface and become a gas — just as water becomes water vapour.
These gas particles move very fast and in all directions.
Because a gas spreads out into the entire available space, they travel out of the kitchen, along the passage and into every room.
They reach our nostrils, and we recognise the smell of the tadka long before we see the food.
Why this example is placed here in the chapter: it is a direct proof of the gas property that the class has just learnt. In the book's own words — the smell of yummy food from cooking spreads through the air and reaches our nostrils, even if we are not in the kitchen. Solids and liquids cannot do this; a spoonful of hot dal on the table stays where it is put, but its smell reaches everyone.
Check it yourself: Open a bottle of perfume or crush a few curry leaves in one corner of a room and stand still in the opposite corner. In half a minute the smell arrives — and it arrives sooner on a warm day, because the particles move faster when it is hotter.