What are the three states of water?

Are ice and water really the same thing?

Ice feels hard and you can hold it in your hand. Water runs through your fingers. So are they different substances? Try this: leave an ice cube in a cup on the table. In a while there is only water in the cup. Now put that water in the freezer and it turns back into ice.

Nothing was added and nothing was taken away. So ice and water are the same substance, water, in two different forms. Scientists call these forms states.

What are the three states of water?

In daily life we meet water in three states:

State	What we call it	Where you see it
Solid	Ice	Ice cubes, hailstones, snow
Liquid	Water	A glass of water, rain, a river
Gas	Water vapour	All around us in the air, though we cannot see it

How do the three states behave?

You can test this at home with a bowl, a box and a plate.

• Shape. Move an ice cube from a round bowl into a square box. It keeps its own shape. Pour water from a tall glass into a flat plate. The water takes the shape of whatever holds it, so it has no fixed shape.
• Flow. Water flows from one container to another. Ice does not flow.
• Spread. Spill a little water on a clean floor and it spreads out, but the amount of water stays the same: its volume does not change. Ice does not spread.

Water vapour has no fixed shape either, and it spreads out to fill all the space it gets. When a mopped floor dries, the water vapour mixes into the air of the whole room. In the same way, the smell of food being cooked reaches you in another room, because smells travel through the air.

Water vapour: the invisible state

Water vapour is present even at room temperature, but it is invisible. Water from drying clothes, mopped floors and our sweat keeps adding vapour to the air around us.

What about the white “smoke” above a pot of boiling water or a hot dosa pan? That is steam. Steam is water vapour, but the white part you see is made of tiny droplets of water that form as some of the vapour cools. Pure water vapour cannot be seen.

How do we change the state of water?

To go from ice to water, and from water to water vapour, we must supply heat. To go the other way, we must cool it.

Change	Name of the process
Solid → liquid (ice → water)	Melting
Liquid → solid (water → ice)	Freezing
Liquid → gas (water → water vapour)	Evaporation
Gas → liquid (water vapour → water)	Condensation

You can see all four at home. An ice cube melts on a plate. Water freezes in the freezer. Wet clothes dry as their water evaporates. Drops of water collect under a lid over a pot of boiling water as the vapour condenses. Evaporation even happens without heating, only more slowly: a puddle dries on a cool day too. Learn more in evaporation and condensation.

Do other substances have these states too?

Yes. A candle is made of wax: near the flame the wax melts into a liquid, and away from the flame it cools and turns solid again. Ghee and coconut oil are liquid on a hot day but often turn solid in winter.

Look around you for more examples:

• Solids: stone, wood, glass.
• Liquids: milk, oil, juice.
• Gases: air, which contains oxygen and carbon dioxide.

So the idea of solid, liquid and gas is not only about water. Many substances can exist in different states, depending on how hot or cold they are.