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Investigation Question 2:
How does temperature affect air pressure?
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What To Do
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Setting the
Scene
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Put two tennis balls into the refrigerator for two hours. Keep the third
ball at room temperature. Take one ball out of the refrigerator and show
it to your students with the room temperature ball. Tell them which is
which and ask them to observe what happens to the balls when you drop
them. Drop the balls at the same time from several feet up. Ask students
which ball bounced higher and why. Next, drop the second ball from the
refrigerator, but don't let the students know if it is warm or cold. Ask
them to infer from the ball's behavior whether it has been in the refrigerator
or not.
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Presenting the Investigation
Question
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Introduce your students to the investigation question: "How does
temperature affect air pressure?"
Have your students discuss the question in pairs, then in groups, and then as a whole class. Record their answers on the flipchart.
Have your students brainstorm ideas about how this investigation question could be investigated.
- Design an experiment that could be used to test the investigation question.
- What materials would be needed?
- What would you have to do?
- What would be measured?
- How long would the experiment take?
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Assessing What Your Students Already Know
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Students may have had experiences with sports balls (soccer or beach
balls) that get smaller and less firm in the winter time. They may have
also noticed that tennis balls don't bounce as high in cold weather as
they do in warmer weather. They may not, however, have connected this
with air pressure and temperature. This investigation will help them to
make that connection.
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Exploring the Concept
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- This is best to do as a demonstration with student help. Blow
up both balloons to the same size. Show the students how to use the
tape measure to measure the circumference of each balloon. (Alternatively,
mark a piece of string with the circumference of one balloon, and attempt
to duplicate the circumference on the second balloon.) The balloons
should be as identical as possible in circumference before tying the
tops.
- On the board or flip chart, ask a student volunteer to record the
circumference in inches for each balloon using the balloon color for
identification.
- Immerse one of the balloons in the bowl of ice water and the other
balloon in the bowl at room temperature. Wait 10 minutes.
- Ask a student to re-measure the circumference of each balloon, and
record this measurement using the color of each balloon for identification.
(The balloon in cold water will be noticeably smaller in size.)
- Ask students to write down any ideas they might have to explain what
they saw.
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