The Water Cycle

The water on Earth is always on a journey. It moves from oceans and lakes up into the sky, forms clouds, and falls back down as rain or snow. This never-ending journey is called the water cycle, and it is powered by energy from the Sun.

When the Sun heats water in seas, rivers and puddles, it turns into an invisible gas called water vapour and rises up into the air. This step is called evaporation. The warmer it is, the faster water evaporates — which is why puddles vanish quickly on a hot day.

High in the sky the air is much colder. The rising water vapour cools down and turns back into tiny liquid droplets. These droplets gather together to form clouds. This change from gas back into liquid is called condensation.

When the droplets in a cloud join together and grow too heavy to float, they fall back to Earth. We call this precipitation. It can be rain, snow, sleet or hail, depending on how cold the air is on the way down.