LAB: "CAN SWEAT"
2014-15
PURPOSE: The temperature of air helps determine its ability to condense water vapor or evaporate water. In this lab you will
discover where "can sweat" comes from and how it relates to cloud formation.
MATERIALS: metal can, thermometer, ice, room temperature water, plastic spoon
PROCEDURE:
• Read the entire lab before beginning the lab.
• Read your thermometer to get the room air temperature. Record this on the data table.
• Fill the metal can half full of room temperature water, put the thermometer in it (never take it out), and drop ice in it a little at a
time. Adding too much ice will wreak havoc will the results.
• Gently stir until a "can sweat" (mist) begins to form on the outside of the can. Do not wait until the “can sweat” begins to drip
down the side of the can. For the best results wipe your finger across the can and when it first leaves a mark, the mist has started to
form.
• Read the thermometer when the "can sweat" (mist) first appears and record this temperature.
• Remove the ice from the can with the spoon and allow the water in the can to warm up. Record the temperature when the "can
sweat" (mist) first disappears. The mist will begin to evaporate at the top, therefore pay close attention to how high up the can the
mist is.
• Average the temperatures at which the "can sweat" (mist) appears and disappears.
DATA TABLE:
1. Room air temperature = ________ °C
2. Temperature at which the "can sweat" (mist) forms = _________ °C
3. Temperature at which the "can sweat" (mist) disappears = _________ °C
4. Average temperatures from #2 and #3 = _______ °C
ANALYSIS: Answer the following questions in complete sentences where there is sufficient room.
1. Which can hold more water vapor (water as a gas); warm or cool air ? Explain why.
2. What happens to water vapor when the air it is in cools down ?
3. What happened to the temperature of the water inside the can when you added ice ?
4. What happened to the temperature of the can when you added ice ?
5. What happened to the temperature of the air next to the outside of the can when you added ice ?
6. Where did the the water that forms the "can sweat" (mist) on the outside of the metal can come from ?
7. Explain what causes the "can sweat" (mist) to form on the outside of the metal can ? Explain this completely.
8. As the air warms up after dawn, would fog (a type of cloud formed at or near the earth’s surface) more likely form or disappear ?
Explain your answer.
9. As warm air rises in a low pressure area, the temperature of the air cools. Would this tend to form clouds or evaporate them ?
Explain your answer.
10. As cool air sinks in a high pressure area, the temperature of the air warms. Would this tend to form clouds or evaporate them ?
Explain your answer.