Three states of water

In daily life, water is found in three states: ice (solid), water (liquid) and water vapour (gas). Heat ice and it melts into water; heat water more and it becomes water vapour. Compare them by shape, and by whether they flow and spread.

Ice (solid) keeps its shape, whatever container it is in: an ice cube is the same shape in a tray, a tub or a glass. It does not flow or spread.

Water (liquid) flows and has no fixed shape: it takes the shape of its container. But its volume stays the same. Pour 1 litre from a jug into a wide tub: it spreads out, but it is still 1 litre.

Water vapour (gas) spreads out through all the space available. Gases have no fixed shape. Water vapour is in the air around us even at room temperature, though we cannot see it. (This is also why leaking cooking gas is dangerous: it quickly spreads through the whole house.)

Other things come in these states too. Wax, oil and ghee can be solid or liquid. Stones, wood and glass are solids. Milk and oil are liquids. Oxygen and carbon dioxide are gases. You can smell food cooking without going into the kitchen, because the smell spreads through the air and reaches your nose.