Water can change
Water is special because we can see it in all three states. It can be a solid (ice), a liquid (water) and a gas (water vapour). Heating and cooling make water change from one state to another.
Key idea
Heating adds heat and makes water melt or boil. Cooling takes heat away and makes water freeze or condense.
The changes
Melting is ice turning into water when it is heated. Freezing is water turning into ice when it is cooled. Boiling (or evaporation) is water turning into water vapour when it is heated. Condensation is water vapour turning back into water when it is cooled, like the drops on a cold glass. Remember that the water is still water in every state — only its state changes, not the water itself.
Example
Leave an ice cube on a plate in a warm room. Heat from the room makes it melt into water. Put that water in a freezer and it turns back into ice. This shows how heating and cooling change the state of water.
Remember
- Ice → water = melting (heating).
- Water → ice = freezing (cooling).
- Water → vapour = boiling/evaporation (heating).
- Vapour → water = condensation (cooling).