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Discovering how cooling a liquid turns it back into a solid.
Have you ever wondered why your favorite juice turns into a hard, crunchy popsicle after sitting in the freezer for a few hours?
Think about the water you drink. It is a liquid. Liquids are runny and wet. They do not have their own shape. Instead, they take the shape of whatever container they are in. If you pour water into a round bowl, the water becomes round! If you pour it into a tall glass, it becomes tall. Water likes to move and flow freely.
Quick Check
If you pour water into a heart-shaped tray, what shape will the water be?
Answer
The water will be shaped like a heart.
When we want to make ice, we put water into a very cold place, like a freezer. The freezer takes away heat from the water. This is called cooling. When water gets cold enough, it stops flowing. It starts to get hard and stick together. We call this change freezing. Freezing turns a liquid into a solid.
1. Fill a plastic tray with liquid water. 2. Place the tray in the freezer where the temperature is below (). 3. Wait a few hours for the freezer to take the heat away. 4. Take the tray out and see that the water is now hard ice cubes!
Quick Check
What do we call it when a liquid turns into a solid because it got cold?
Answer
Freezing.
Once water is frozen, it is a solid. Unlike liquids, solids keep their own shape. If you take an ice cube out of a tray and put it on a flat plate, it stays a cube! It does not spread out like liquid water does. Solids feel hard and firm when you touch them. They are also very cold to the touch because the heat has been taken away.
Imagine you have a cup of orange juice and an orange popsicle. 1. The juice is a liquid; you can stir it with a spoon. 2. The popsicle is a solid; you can hold it in your hand without a cup. 3. Both are made of the same stuff, but the popsicle is frozen!
In the winter, the air gets very cold. 1. The cold air takes heat away from the water in a pond. 2. The top of the water reaches . 3. The liquid water turns into a sheet of solid ice that you can walk on!
What happens to water when it loses heat in a freezer?
Which of these is a property of a solid?
Freezing is when a liquid changes into a solid.
Review Tomorrow
Tomorrow, try to explain to a friend what happens to water when it gets very, very cold.
Practice Activity
With an adult, put a small toy in a cup of water and freeze it. Watch how the liquid water turns into a solid 'ice jail' for the toy!