Water is the most important liquid we know. It is everywhere we look. Water is in the ground and in the air that we breathe . All animals, plants and humans need water to survive . Water has formed our earth since its beginning. It also prevents the earth from becoming too hot or too cold. Water never disappears . We use the same water over and over again.
Chemistry of water
Water consists of very small molecules. Each of them has two hydrogen atoms and one oxygen atom. The chemical formula of water is H20.
Water can be a solid , a liquid or a gas, depending on the temperature it has. At 32° F (0° C) water freezes and turns into ice. It expands and becomes lighter. As a result ice floats on water. That is why you should let water out of pipes during the wintertime because it may freeze and burst the pipes. At 212°F (100°C) water boils and escapes as a vapour into the air. Between these two states water is a liquid. Most of the world’s water is in liquid form. It can be found everywhere on earth.
Water molecules always move. In ice they are very far apart from each other. They move very slowly or often not at all. Molecules in water vapour move very quickly.