Lesson 2 Page 3
Explore: How Can We Show the Properties of Air?
Air is all around us. It takes up space, it has mass, it exerts pressure, and it can be compressed. You were able to observe this in the previous activities. Sometimes, we forget that air can be a very powerful tool. We cannot see air because the particles are so very small. But, if we get enough of these particles together to push against something, they might exert enough pressure to be extremely useful.
Air pressure is used in many ways: your bike tires contain air, air bags can protect you in a car collision, and you might fly somewhere soon (in an airplane, of course!). These things make use of air pressure to work.
Career Connection
Air brakes use air, instead of braking fluid (hydraulics), to control the brakes that stop large trucks and trains. Hydraulic brakes used in normal vehicles can leak and cause the brakes to fail. That is why air brakes usually are used in trucks or trains that carry heavy loads where brake failure can be extremely dangerous. Drivers and mechanics need special training in how to operate and maintain air brakes. You can learn more about air brakes by visiting this website: " How Air Brakes Work".
Technology Connection
Fire and rescue crews sometimes use inflatable airbags to lift heavy vehicles after collisions, or upsets. These use the same principle of air pressure you used to lift the book using the Ziploc bag but on a much larger scale. See an example of this cool tool at work.
Notebook: How can we show that air takes up space (volume), exerts pressure, can be compressed, and has mass (weight)?
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Check Your Answers
| Activity | What Happened? | Can you explain what happened? How was AIR involved? |
| Paper Chase | Crumpled ball of paper fell faster than the flat sheet of paper fell. | The flat sheet of paper had a larger surface area; therefore, more air pushed up against it as it fell. The crumpled ball of paper had less air pushing against it, so it fell faster. |
| Balloon balance | The balance tips towards the inflated balloon when the other balloon is popped. | When one balloon was popped, the air was released from that side. Now, the balanced tipped towards the side with the inflated balloon because the inflated balloon weighed more. |
| Air Underwater | Ping-pong ball sinks into the pot when the cup is placed into the water. The paper in the cup stays dry. | The air inside the cup pushed down on the water to cause the ping-pong ball to sink. The air inside the cup prevented water from going inside the cup and wetting the paper. |
| Air Compressed PhET Simulation | What do the gas particles do when you pump them into the container? | They move around and start to fill the container. They bounce off each other and the walls of the container. |
| Air Compressed PhET Simulation | What happens when you make the container smaller? | The gas particles are compressed together to fit into the smaller space. |
| Air Compressed PhET Simulation | What happens when you make the container bigger? | The gas particles spread out to fill the larger space. |
The air inside the balloon causes it to inflate.
The air inside the cup keeps the water out and keeps the paper dry.
The air pushes against the flat sheet of paper to make it fall slower.
The air inside the cup pushes against the water and ping-pong ball to cause the ball to sink.
After one balloon is popped, the loss of air on that side caused it to weigh less; therefore, the balance tipped. If air had no weight, popping the balloon would have no effect.