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Talk with the students about air pressure, utilizing the material
that is in the Teacher Text and Science Concept. Make sure that each
child has at least some understanding of the nature of air pressure.
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Hand out to each student: a plastic cup half-filled with water and a
drinking straw.
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Ask each student to suck some water up into the straw and quickly
cover the top of the straw with their finger.
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Then ask the students to lift the straw out of the plastic cup. What
happens? (Nothing). No air can get into the top to allow the water to
come out.
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Have the students next lift their finger off of the straw. What
happens now?
Now the air can get into the top of the straw, and the water can flow out
because of gravity.
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After the experiment is completed, review with the children what has
happened.
(The pushing force of the air is called air pressure and this is what got
into the top of the straw, and the water can flow out because of
gravity.)
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