Dry ice!

To conclude our unit on Matter, we investigated Dry Ice!  I purchased 25 pounds of Dry Ice in pellet form from the Acme Dry Ice Co. in Cambridge.  Dry Ice is frozen carbon dioxide, a normal part of our earth's atmosphere. It is the gas that we exhale during breathing and the gas that plants use in photosynthesis.

It is also the same gas commonly added to water to make soda water.  Dry Ice is particularly useful for freezing, and keeping things frozen because of its very cold temperature: -109.3°F or -78.5°C.  Dry Ice is widely used because it is simple to freeze and easy to handle using insulated gloves.

Dry Ice changes directly from a solid to a gas -sublimation- in normal atmospheric conditions without going through a wet liquid stage. Therefore it gets the name "dry ice."

Dry Ice Challenges!

You and your partner will try the following Dry Ice activities. Follow the proper science safety rules at all times and do not pick up the dry ice with your hands! Write your observations for each activity. When done, answer the questions below and do two sketches of activities we did today on the back of this paper.

A. Place your piece of dry ice on your desk top and watch it. Did it melt? What do you observe?
B. Put a tiny piece of dry ice into cold water. Does it sink or float? Try poking it with your tweezers. What can we infer about its density as compared to water?
C. Put several drops of water on a piece of dry ice. Observe.
D. Press the metal paper clip against the dry ice. Observe.
E. Compare dry ice in hot and cold water.

Questions
a. What is dry ice made of?
b. What happens to solid dry ice at room temperature?
c. Are the molecules in “solid dry ice” different from the molecules in “dry ice gas”?
d. What makes the solid carbon dioxide change to gaseous carbon dioxide?