The Weight of Air

 

Difficulty: Easy 1/3

Danger: Safe 1/3

Equipment Needed

• a balloon
• a kitchen scale

Have you ever been traveling and felt your ears pop? This usually happens when you are changing your altitude quickly like when an airplane takes off or lands, or when you are driving up and down mountains. This happens because air has weight. Yes, you read that right, air has weight! We usually don’t talk about the weight of air, we usually talk about pressure but these two are related. Pressure is how much force there is spread over how much area. Weight is the force of gravity, so what we feel as air pressure is usually the weight of the air above us. You can test the hypothesis that air has weight in this experiment.

Hypothesis: Air has weight. (If you think I’m crazy, you could choose a different hypothesis if you like.)

First, you need an empty balloon and a kitchen scale. Place the balloon on the scale and wait for the number on the scale to settle down. If your scale allows, hit the “zero” or “tare” button so that your scale shows no weight when the balloon ALONE is on the scale. This will make your final reading the true weight of the air inside the balloon. If your scale doesn’t have a “zero” or “tare” feature than write down the weight shown when the balloon ALONE is on the scale.

Next, take the balloon and fill it with air, not helium, just regular air. You blow up the balloon. Tie the end of the balloon so the air stays inside your balloon. Now place the balloon back on the scale. What does the scale read? If you were able to “zero” or “tare” your scale earlier than what you see is the actual weight of the air. If you could not “zero” or “tare” your scale than write down the number you see now, it should be bigger than your first number. This number being bigger tells you that by putting air in the balloon you added weight to your balloon. The difference between these two numbers will give you the weight of just the air.

There isn’t really a separate explanation to this experiment but the Extra Credit section gives you a chance to see more.  Click below to see the Extra Credit section…