Dry Ice Demonstrations

SAFETY NOTE: Do not hold the dry ice. It is extremely cold and can damage (burn) your skin. Wear gloves to protect your hands due to the extremely cold temperature. Wear safety goggles when breaking dry ice or cover it with a towel to contain the dry ice pieces.

Carbon dioxide (CO2) usually is a gas. However, it can be made into a solid through freezing. We call this solid "dry ice" because it does not melt! It changes from a solid straight to a gas. When matter changes from a solid straight to a gas we call this process sublimation.

Dry ice uses: freezing/preserving food, shipping cold materials, industrial cleaning, special effects

Demo #1
1. Place the dry ice in water. Include drawings/observations to describe what happened.
2. What happened to some of the water around the dry ice? ____________________________
3. Does the carbon dioxide gas leaving the container feel cool or warm? __________________
4. Does the carbon dioxide rise or sink when leaving the container? ______________________
5. What could you infer about the density of cold and warm gas?________________________
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Demo #2 (Safety: a loud noise may occur,
to protect your ears cover them)
6. Have your teacher place dry ice in a florence flask.
7. Immediately place a balloon over the opening of the florence flask.
8. What do you think will happen?
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9. Describe and draw what happened. You may want to draw several pictures showing how it changed over time. (use colored pencils)

10. What is this process called? (solid to a gas) _____________________________________
11. What occurred on the outside of the florence flask? _______________________________

Background Information
The amount of water vapor that air can hold depends on the temperature of the air.
Warm air will hold more water than cool air.
When the air is holding all of the water vapor that it can it is said to be saturated.

The actual amount of water vapor in the air compared to the amount in saturated air is known as relative humidity. When the relative humidity is 100% the air is saturated and water vapor will begin to condense. This leads to rain, fog, dew.

The dew point measures the temperature at which water vapor will begin to condense for a given amount of water vapor in the air. The higher the relative humidity (the amount of water vapor present in the air -- Meteorologists use relative humidity to help predict snow, rain, or icy conditions) the higher the dew point.

If the temperature of the air is suddenly dropped below the dew point, water vapor will begin to condense. This is what causes the water droplets on the outside of cold soft drink cans. Notice water droplets do not form on the outside of warm soft drink cans.

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