SOLIDS, LIQUIDS AND GASES
Chemicals may be solids, liquids or gases. Water is a liquid. When water is cooled to below 0°C it freezes and forms ice, a solid. When it is heated to 100°C it boils and changes to steam, a gas. We say that water can change its ‘state’.
A chemical’s state depends on its temperature. Solids may turn to liquids and gases and then back to solids again, as the temperature rises and falls. We usually see metals and rocks in their solid state. When they’re heated, they become softer. If they’re heated to a high enough temperature, they melt and become liquid.
Ice
Because the molecules in a solid, such as ice, are held firmly together and can only move about a fixed point, they have a definite shape.
Water
As a liquid, water molecules can move around more freely. The ‘shape’ of the water depends on the container.
Water vapour
The molecules in steam can move freely in all directions, spreading further and further apart until they fill their container.
In the Arctic, the temperature is so cold that sea water freezes into huge solid glaciers.
Steam is given off by cooling towers. The water vapour molecules move freely and spread apart.
Picture Credit : Google