Water exists in three states - solid, liquid, and gas - and can change between these states when it gains or loses heat. It freezes into ice at 0°C when it loses heat, melts back into liquid water when it gains heat above 0°C. Water boils into steam at 100°C when sufficient heat is added, and condenses back to a liquid when steam cools below 100°C losing heat. The rate of evaporation depends on factors like wind, temperature difference, and surface area.

1. Changing States of Water
Water exists in three states
Water can changes its state when it becomes colder (loses heat) or
hotter (gains heat)

2. When water loses heat or gains heat
When water is cooled to 0 °C, it changes to ice
Water changes from
liquid to solid state
Freezing
loses heat
The freezing point of pure water is 0°C

3. When ice cube at 0 °C gains heat, it changes to the liquid state
Water changes from
solid to liquid state
Melting
gains heat

4. Freezing
Melting

5. When we heat water to a temperature 100 °C, it changes the
liquid water to steam
Water changes from
liquid to gaseous
state at 100 °C
Boiling
The boiling point of pure water is 100°C

6. When we heat water at temperature below its boiling point, the
liquid water changes into water vapour
Water changes from
liquid to gaseous state
at temperature below
100 °C
Evaporation
gains heat

7. When water vapour and steam are cooled, it condense into
liquid water
Water changes from
gaseous to liquid state
Condensation
loses heat

8. How quickly or slowly evaporation takes place is known as the
rate of evaporation
The rate of evaporation depends of:
- wind
- temperature difference
- surface area

9. Condensation
Evaporation