Water can be a solid,
gas. When it is a solid it is ice or snow. When it is a gas it is water vapor, or steam.
Changing the Temperature of Water
Water comes in three different forms. It can be a solid (ice) a liquid (water) or a gas (water vapor or steam). To change the water from one form of matter to another you need to add or take away heat.
When you investigated your ice cubes, what form of matter was the ice cube? What about after it melted? When you heated one on the stove, the water disappeared.
What form had it turned into?
Water changes form at different temperatures. It becomes a solid at 00C. It becomes a gas at
Adding Heat to Water
If you add enough heat to water, it will turn into a gas. That gas is known as water vapor, or steam. Water vapor is difficult to see. The best way to see it is to boil a pot of water and shine a flashlight above it. The steam will make a shadow on the wall behind the stove.
If you have water in its solid form (ice) and you add heat it will turn into a liquid. That change is easy to see.
If you start with an ice cube and heat it, it will turn into water (liquid). If you keep heating it, it will turn into a gas (steam).
Taking Heat Away from Water
If you take heat away from water, it changes form. If you start with a liquid and remove heat, it will become a solid. That is what happens when you put an ice tray, full of water, into the
If you start with a gas and remove heat, it becomes a liquid. That is what happens in the bathroom when you take a shower. Have you ever noticed that the mirror gets steamed up when you take a hot shower? That is because the hot water vapor meets the cold mirror. The heat is taken out of the vapor and it turns back to water.
There are special words to describe what happens to water when it changes form. When water changes to a gas we say it
evaporates. When water vapor changes to a liquid we say it
condenses. When you boil the kettle, the water evaporates and turns into steam. When the steam meets a cold surface, such as a mirror, the windows, or ceramic tiles, it condenses and turns back into water.
Water changes from solid to liquid to gas and back again. You can change it from one form to another by adding or taking away heat. These changes are
reversible. If you can make a change, and then change it back to the way it was, the change is reversible.