Water is made of tiny particles. Each one is so small that you can’t see it even with the most powerful microscope. Pure water has no colour, no taste and doesn’t smell of anything.

Water exists in three forms on the Earth

Water is found as a:

• solid (ice, hail, snow or frost)
• liquid (in lakes, oceans, rain, dew, fog or mist)
• gas (steam or water vapour - "invisible" water in the air).

Water can change from one form to another with a change in temperature.

Most of the water found on the Earth's surface is in liquid form. The blue ocean colour you see is due to reflections from the sky. Have you ever noticed the colour of the sea change from a sunny day to a cloudy day?

Water is a scarce and precious resource. Around 70 per cent of the Earth's surface is covered by water, in oceans, seas, lakes, rivers and swamps.

An interesting property of ice is that it freezes from the top down. Imagine how fish or other animals and plants would cope if water froze from the bottom up!

Have you or someone in your family ever left a bottle in the freezer. The liquid (mostly water) freezes and expands and often will break the bottle. This is another property which very few things have – expanding when it turns into a solid, most liquids shrink when they cool and become solid.

Unfortunately for us, most of the water on Earth is salty or frozen. Only a very small amount is suitable for us to use in our day to day lives.

Water is the most important and probably the most widely known substance on Earth. But unless there are droughts or floods, most of us don't think about it much.