Water can swap between a solid, a liquid and a gas depending on its temperature. Liquid water is what we see and use most often – we use it to wash, clean, cook, grow plants and drink. Just about everything really!

Water on Earth is mostly in the oceans, along with the polar ice caps, rivers, lakes and clouds. The total amount of water on Earth is more or less stable over time, but the exact location of the water on Earth is always changing. For example, some days the weather is dry and some days it’s pouring with rain. This movement of water around the planet is called “the water cycle”.

The water cycle is impossible without heat from the sun. When the sun heats water it evaporates, changing from a liquid into a gas called water vapour. As water vapour rises, it cools and condenses back into tiny droplets of liquid water. If enough of these tiny droplets condense in the air they might form clouds, and if enough clouds form then the liquid water falls back to the ground as rain. The cycle then restarts and continues forever.

See the water cycle in action at home or in class with this experiment!