Why water is a good example for all states of matter?
Water is unique because it is the only natural substance that can exist in all three states of matter at the temperatures normally found on Earth! Water is usually a liquid, but when it reaches 0° C (32° Fahrenheit (F)), it freezes into ice. (Ice is the solid-state of water.) When the water reaches 100° C (212° F), it boils.
When it begins to boil, some of the water turns into steam. (Steam is the gas state of water, and is also called water vapour.) When steam comes into contact with cool air (which reduces energy), it can condense back into water droplets (liquid again). Those water droplets could then freeze into (solid) ice.