Lesson

Materials

• Beaker
• Tongs
• Food coloring
• Pipet
• Liquid soap
• Warm water

Procedure/Analysis

1. Obtain a piece of dry ice in a beaker from your teacher.
2. Tightly cover the beaker with the palm of your hand so no gas can escape.
   1. What do you feel on the palm of your hand (there are two things)?
   2. Why is this happening?
   3. Why does a substance as a gas take up more room than it would as a solid?
3. Make three observations about the dry ice (you can put the dry ice on the table. Hold it with the tongs only, do not handle it with your bare hands!)

3. 1. What two states of matter are present?
   2. In what direction is the vapor moving? Why do you think the vapor is moving in that direction?
   3. The CO₂ vapor from the dry ice is (less / more) dense than the surrounding air. Explain how you know.

4. Lay your pen/pencil down on the table top. Using another pen/pencil, slide the block of dry ice across the table. Attempt to have the block of ice come to rest as close as possible to the pen/pencil laying on the countertop.
   
   1. Why does dry ice slide so easily? (Is it because ice is slippery, is it because it is riding on a layer of gas, or is it because it is riding on liquid?) Explain your choice: how do you know?
      
5. Using a pipet, make a quarter-sized puddle of water on the counter. Using tongs, place a piece of dry ice in the puddle and move the dry ice around. Write down your observations of what happens to the water under the dry ice.
   
6. Warm the tip of the tongs with your hand and squeeze the piece of dry ice with the tongs. What causes the noise?
   
7. Warm a coin with your hands and then press the edge into the dry ice until a crevasse is formed. Warm the coin again and place it into the crevasse. Why does the coin “shiver?”
   
8. Fill your beaker halfway with warm water. Using the tongs, place the dry ice into the beaker. Make three observations of the dry ice in water.

9. Is the CO₂ gas more or less dense that water? How do you know?
   
10. Predict: what will happen to the vapor when a drop of food coloring is dropped into the water? Prediction:
11. Place food coloring in the water and make two observations.

12. Why did these things happen?
13. Predict: What will happen when liquid soap is added to the beaker of water? Prediction:
14. Place three drops of liquid soap into beaker and then make two observations:

15. Why did these things happen?
    
16. The time taken for the dry ice to completely sublime depends on temperature. If possible, do this demonstration in a sunny position on a dark plate, or even a piece of black cardboard to speed up the process. Place an ice cube and a few pellets of dry ice side by side on your table. Wait a couple of minutes. Why is this substance called dry ice?

Conclusion

1. What is dry ice made of?
2. What is the freezing point of dry ice (^oF and ^oC)?
3. What is the process called when a solid changes directly into a gas?
4. Write a paragraph about your experience in class today (five-eight sentences). Also include ideas of how humans could use dry ice to their advantage (~two sentences).