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RECAP THE CONCEPTS
The water cycle provides living things with a continuous supply of fresh water.
The Sun is the main source of heat that causes water to evaporate from water bodies.
The water vapour rises to the sky, loses heat to the cooler surrounding air and condenses into tiny water droplets (clouds).
When the water droplets combine and become too heavy, they will fall back to the ground as rain.
When water gains heat:
Occurs when solid water (ice) changes into liquid water.
When melting, ice gains heat but its temperature remains constant at melting point (0°C).
Occurs when liquid water changes into gaseous water (water vapour).
Water gains heat from its surroundings and evaporates.
This can occur at any temperature (between 0°C and 100°C).
Factors that affect the rate of evaporation include:
presence or strength of wind,
exposed surface area of water and
temperature of surroundings/water.
Occurs when liquid water changes into gaseous water (steam).
When boiling, water gains heat but its temperature remains constant at boiling point (100°C).
The white cloud observed above a pot of boiling water is made of tiny water droplets (not steam).
When water loses heat:
Occurs when liquid water changes into solid water (ice).
It occurs at a constant temperature known as freezing point (0°C).
Occurs when gaseous water (water vapour or steam) changes into liquid water (water droplets).
Water droplets form on the outer surface of a glass of cold water.
Water droplets form on the inner surface of a glass of hot water.
White clouds form above a pot of boiling water. This is because steam loses heat to the cooler surrounding air above the pot of boiling water and condenses to form water droplets.