Teachig Air: Mixture of Gases

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This pdf contains content related to the Air which is the general name for the mixture of gases that makes up the Earth's atmosphere.
1. Lesson 1: What is Air?
Air: A Weighty Topic
Background Information
Air is essential for life on Earth. Without air to breathe, we
could not survive, but what exactly is air?
Air is all around us but it is difficult to investigate because we
cannot see, taste, or touch it. With this lesson, the students will
become familiar with some of the different properties of air by
participating in a few simple hands-on experiments.
The students will find that even though air seems thin and
light, it has weight. For example, the air inside a bus weighs as
much as one of the passengers! Air is one thousand times lighter
than water. This means that a bathtub full of air weighs about
the same as a cupful of water. Scientists use complex and
delicate instruments to measure the weight of air. This activity
will allow the students to use everyday materials to weigh air.
Even though we cannot feel it, there is more than 14 pounds
of air pressing on every square inch of our skin! Air pressure is a
powerful force that is caused by a layer of air called the
atmosphere which surrounds the earth. Air pressure is measured
with an instrument called a barometer.
After completing the lesson, the students will understand the
1. Air is all around us.
2. Two objects cannot occupy the same space at the same time.
3. Air is matter because it takes up space and has mass
4. Air presses down.
2. 5. Air is fluid and takes the shape of the container it is in.
Materials Needed
1. A clear, empty squeeze bottle
2. A plastic bag
3. A plastic (watertight), shoebox-size container for each group
of four students
4. One clear plastic cup per group
5. One or two paper towels per group
6. Two balloons of equal size per group
7. One wire hanger per group
8. 12 inches of thread per group
9. One ruler per group
10. One balance scale
11. One Scientific Procedure Sheet per child
1. Before class, fill plastic containers with water.
2. Organize group materials.
1. Begin the lesson by going around the room and squeezing the
“empty” squeeze bottle at all the students. They will jump as the
air rushes out of the bottle toward them. Ask the students if the
bottle is really empty and what is coming out of the bottle. The
students will tell you that air was in the bottle. Show the
students that the air flows back into the bottle the second you
stop squeezing it. (Air is fluid.)
3. 2. Ask the students to predict what shape air will take if you pull
a plastic bag through the air. (Air takes the shape of its
container.) Demonstrate that air is all around the students by
pulling the plastic bag through different areas of the classroom-
the closet, inside a desk or file cabinet.
3. To prove that air takes up room, each group of four students
needs a plastic container filled with water plus the cup and
paper towel. Each group will ball up the dry paper towel and
place it securely in the bottom of the cup.
4. Ask the students to predict what will happen to the paper
towel if they place the cup into the water upside down.
5. Have the groups invert the cup and hold it straight down as
they slowly submerge it in the water. They will then pull it out of
the water still keeping it totally vertical.
6. Have the groups remove the paper towels. They will find that
the paper towels are still dry.
7. Ask why the paper towel stayed dry. Elicit that there was air
taking up room in the cup along with the paper towel. The air
prevented water from entering the cup, because two objects
cannot be in the same place at the same time.
8. To show the effects of air pressure, have each group place a
ruler on their tables so that about one third of the rulers extend
over the edge. The students will tap this end gently. They will
find that the rulers fall off the tables.
9. With the rulers in the same positions on the tables, the
students will place a sheet of copy paper or newspaper over
them. Have the students tap the rulers with the same degree of
force as used the first time. This time the ruler should not fall.
4. 10. Elicit that air was pressing on the larger surfaces of the
paper and therefore the rulers as well. This pressure was greater
on the papers than on the ruler by itself.
11. To demonstrate that air has weight, ask the students to
predict which is heavier, an inflated balloon or an empty balloon.
Many students may predict that the empty balloon is heavier,
because they associate filled balloons with “floatability” in the
12. Demonstrate that two empty balloons are the same weight
on the balance scale.
13. Have the groups use the wire hanger, thread, and two empty
balloons to prove that air has weight. Do not tell them how to do
it. It probably will not take long for the students to figure out
how to turn the thread and hanger into a balance scale. (They
can tie equal lengths of thread to each end of the hanger. Then
tie the end of each thread around each tied off balloon end. To
use the balance, the students can raise it by placing a pencil
under the hanger hook.) After they make their balance scale,
they can compare the weight of an inflated balloon and an empty
The balloon filled with air will make its side of the scale tip
slightly lower because the air in the balloon has weight.
1. The students can complete the Scientific Procedure Form for
the experiments. The steps of the scientific method can be
2. The students can design their own experiments to prove each
of the properties of air. The students can share their experiment
procedures and results.
5. Glover, D., (1987). Flying and Floating. New York: Kingfisher
Walpole, B., (1988). 175 Science Experiments. New York:
Random House.
Weiner, E., (1992). Dirt-Cheap Science. New York: Scholastic.