Changing
States
of Matter

Energy (heat is a form of energy) is added (absorbed) to cause melting and evaporation
Energy is released to cause freezing and condensation.
Energy is transferred in all changes of state.

Carbon dioxide usually is a gas. However, it can be made into a solid. We call this "dry ice." It is called this because it does not melt! It changes from a solid to a gas. When matter changes from a solid straight to a gas we call this process sublimation. Dry ice is used to keep things cold.

SAFETY NOTE: Do not hold Dry Ice. It is extremely cold and can damage your skin.

Demo #1
1. Have your teacher place dry ice in a beaker of water. What happpened? Include a drawing and written observations (quanititative and/or qualitative).

2. Does the carbon dioxide gas leaving the beaker feel cool or warm?
3. Does the carbon dioxide rise or sink when leaving the beaker?
4. What could you infer about the density of cold and warm gas?
5. What happened to some of the water in the beaker?


Demo #2
1. Have your teacher place dry ice in a florence flask.
2. Immediately place a balloon over the opening of the florence flask.
3. What do you think will happen? Why?
4. Include a drawing and written observations (quantitative and/or qualitative).
SAFETY NOTE: you may need to cover your ears
the pop of the balloon can be very loud.

5. What is this process called (solid to a gas)?
6. What occurs on the outside of the florence flask?
7. What did the ice do to cause this?
8. Is the inside of the florence flask dry or wet?

|| Back ||