Air and Air Pressure

Mildred 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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