```Air and Air PressureMildred L.Butler               Douglass Math and Science Academy                               543 N. Waller                               Chicago IL 60644                               (312) 534-6176 Objectives:

To find air.
To observe that air takes up space.
To observe that air has weight.
To observe that air exerts pressure.

Materials Needed:

2 - 5 gallon clear aquariums   Equipment per group:
water                          4-sticks
soil                           2-balloons
8-balloons                     1 container with a hole
paper                          water
clear glasses                  1 straw
sticks                         1 pin
cans with holes
straws
pins

Strategy:

1.  Have the students take the piece of paper that is on their desk and fan
with it.  Discuss and have students draw conclusions.  Explain that air
is everywhere.
2.  Place a lump of soil in a container of water and have students observe.
Ask students did they see anything that might indicate the presence of
air in the soil?  Bubbles began to come out of the soil and go up to
the top of the water.  Discuss.
3.  Secure an aquarium or a container and fill it nearly full of water.
Turn one of the glasses upside down under the water. Ask students what
did they observe?  You will see that it stays full of air.  Put the
second glass under the water with the other hand.  Turn the second
glass on its side as you lower it so it fills with water.  Have
students make hypotheses.  Move the two glasses together and tilt the
first glass so that bubbles of air begin to rise into the second glass.
Have the students observe and draw conclusions: water in the second
glass is driven out by air rising from the first glass.  The first
glass fills with water, which replaces the lost air.
4.  Tie the end of one string tightly to the middle of a stick.  Hang the
stick up by the other end.  Slide the string along the stick until it
hangs exactly level.  Blow up one balloon and tie the neck with a
second string.  Blow up the second balloon until it is about the same
size as the first.  Tie a balloon on to each end of the stick.  Slide
the strings along the stick until the stick hangs exactly level again.
Now prick one balloon with a pin and watch.  Have students draw
conclusions: when you burst one balloon, all the air comes out.  The
other balloon with air in weighs more than the empty one, so the stick
goes down.  Now burst the other balloon and the stick will become level
again.
5.  Have students drink some liquid and explain how easily it comes up the
straw.  Then make a small hole in the straw about 2 inches (5 cm) from
the top end and try to drink again.  Ask students to explain why it
took much longer: when you suck through a straw, you lower the pushing
power of the air in your mouth and in the straw.  The air pushing down
on the surface of your drink forces liquid up the straw.

References:

Schug, Ken. Demonstrations given during SMILE, Summer, 1993
Barbara Pawela, Ed Gudziol, Patricia Riley, Therese Donatello,
Resource books, 700 Science Experiments for Everyone, by Gerald
Wendth, Chemistry for Every Kid, by Janice Van Cleave, and
The Know How Book of Experiments.

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