What is water?
What is water?
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 reflection 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% 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. We need water for lots of reasons including:
- Watering plants
- Washing and cleaning
- Recreation (swimming and boating)
- Cooking (don’t forget - water is needed by the plants and animals we eat to live and grow)
Factories (many factories use large amounts of water to help make the things we use every day)
Water usually has other substances dissolved in it. Examples of this include the ocean, our blood and cordials and soft drinks. We cannot always see, or even taste dissolved substances.
Our blood is made up mostly of water. Many things dissolve in the water in our blood. For example, wastes are carried from around our body to our kidneys where they can be filtered out.
A can of soft drink shows how water can dissolve a range of substances - sugar, colouring, flavour and dissolved gases, especially carbon dioxide, which makes soft drinks 'fizzy'.
Water is all around us. It is in the air, in the ground and in every living thing. Do you know that water actually makes up most of our body? Other animals and plants can have even more water than us in their bodies.