Making changes
You can change matter from one form to another by making molecules
speed up and slow down. This project will show you how.
A melting race
Make sure the glasses are at room temperature. Put an ice cube in the
first glass, a small piece of butter in the second glass, and a penny in
the third glass. Leave the glasses for five minutes. Which things have
melted?
Materials
butter (cold)
glasses (3, same size)
ice cubes (2)
jar lid (metal)
pan
penny
water
At room temperature, some of the ice cube melts. The butter softens, but
it doesn’t melt. The penny doesn’t change.
Next, pour one inch (2.5 centimeters) of hot water into the pan. Set the
glasses in the pan and leave them for five minutes. What changes do you
see?
The hot water makes the molecules speed up. Much more of the ice cube
melts. The butter melts, too. But the molecules in the penny don’t speed
up much—it doesn’t melt.
Liquid to gas to liquid
Fill one glass half full with hot water. Set the jar lid on the glass,
upside down. Then place an ice cube in the lid. After five minutes,
remove the ice cube. Carefully lift the lid. What do you see on the side
that covered the glass?
There are drops of water on the lid. Some molecules in the hot water
changed to gas. But when the molecules of gas hit the cold lid, they
slowed down. They condensed and became a liquid again.
