Everything that take up space has mass, even if we cannot see it. This includes the air we breathe in and walk around in every day. When the air is calm, we do not notice it since we just walk through it, cannot see it, and do not feel it. When the air begins to move, such as with a breeze, you can feel it moving. Sometimes if it is moving fast enough the air can even push you. We also do not notice this air because it is spread out over a large area (the Earth) that does not confine the air to a small area. Yet, if you blow up a balloon, you see air pressure in action. The air is being pushed into a smaller area even though it wants to spread out. If you let go of the balloon, you will notice it sinks to floor. This is because even though the air in the balloon is the exact same as the air around us, the mass of the balloon itself is greater and causes it to fall.

With these ideas, we can create a balance that showcases that air does have mass.

Supplies

2 Balloons of the same type and brand
Tape
A Ruler, Meter Stick, or Yard Stick
Scissors
String

Step 1: Key Terms

Mass – the amount of matter in an object

Matter – the amount of a substance that is present; how much “stuff” is present

Balance – a device used to measure mass

Pressure – continuous physical force exerted on or against an object by something in contact with it

Step 2: Tie the String Onto the Yardstick

Tie a piece of string that allows the ruler/meter stick/yard stick/clothes hanger to balance evenly when hanging only from the string. If one side is lower than the other, find the center of mass on your finger or move the placement of the string. Secure with tape.

Step 3: Fill Each Balloon Up With Air to Roughly the Same Size and Tie Off.

Step 4: Attach One Balloon to Each Side of the Ruler/meter Stick/yard Stick With Tape.

Step 5: Create Balance

Balance the ruler/meter stick/yard stick/ clothes hanger by balancing the ruler/meter stick/yard stick by holding the string. Notice how the scale is balanced and neither side is heavier than the other. If one side is lower than the other, troubleshoot by filling another balloon as one may be larger than the other. Too much tape on one side may also cause one side to be lower.

Step 6: Cut a Hole

Using the scissors, cut a hole in balloon to allow the air to come out but still be attached to the stick or hanger. If the balloon does pop, be sure to lay the balloon on the side without a balloon.

Step 7: Observe the Changes

Notice how the side with the filled balloon is heavier as it goes downwards. The mass of the balloons becomes negligible because it is equal on both sides. This showcases how the air trapped inside the balloon has a mass.