Air Pressure, does air have mass?

Have you ever watched a weather forecast on the television and seen a map of your area with thick red and blue lines that the meteorologist points to when predicting the upcoming weather? These maps are actually a type of surface weather analysis that shows us many different parts of weather over a particular area at a specific time, based on the information collected from ground-based weather stations. These maps combine the information of air pressure, temperature and humidity to determine where and how weather systems are moving.

Pressure differences in our atmosphere's air masses cause them to constantly shift and change, along with our weather. With all these air masses moving around in our atmosphere, they are sure to collide with each other...and they do! Even though they bump into each other, these air masses rarely mix because of their different densities. Instead, storms and other severe weather phenomena form along the boundaries of the air masses. This area is called a weather front. Four possible types of weather fronts are: 1) warm fronts, 2) cold fronts, 3) occluded fronts and 4) stationary fronts. How do you know which kind of front will form? Well, that all depends on the properties of the air masses that are colliding.

Demonstration: To really understand air mass, we must understand that air has mass. We can use a balloon and a scale to demonstrate this concept. (To begin, zero the scale, then record the mass of the empty balloon. Next, blow up and tie the balloon that was weighed, and place the inflated balloon back on the scale. Record the new mass. Use a roll of tape to keep the balloon from rolling off the scale. Make sure that the scale is zeroed with the roll of tape on the scale as shown in Figure 2). The scale should be able to measure to a tenth of a gram for it to detect the mass of the air in the balloon.)

Materials needed: 5 orange mass cubes, a ten gram mass, a twenty gram mass, a roll of masking tape, a balloon.

Procedure: Make sure the scale is set to grams.  Now take turns checking the mass of the cubes and masses.  Make sure the scale indicator matches the grams you added.  


On a lab sheet, write answers to the following questions:

  1. What is the mass of the empty balloon? _____

  2. What is the mass of the roll of tape and the empty balloon?_____

  3. Inflate the balloon to about 10 inches in diameter, but be careful not to make it burst. Tie it closed!

  4. What is the mass of the roll of tape and the inflated balloon?_____

  5. Math time: What is the mass of the air in the inflated balloon?_____

  6. Can you find the mass of the inflated balloon without having to subtract the mass of the roll of tape?

  1. What is the mass of the air in the inflated balloon using the proper method?_____

  2. What have you learned from this activity about air and air pressure?

Three photos show the demonstration steps of weighing a balloon before and after it is inflated.

Air has mass!