LEARNING GOAL I will conduct experiments to determine that air has mass. I will explain how experimental results provide evidence that air has mass.

Where’s the Air?

Discussion Where does weather happen? –ATMOSPHERE

AIR In our first investigation we used a variety of weather tools to measure weather conditions. Air plays a very important role in the weather. In the next few days we are going to look more closely at air to learn some of its properties.

SYRINGE This is a syringe. You can use it to investigate air. You can work with your syringe alone or with other students, but you should not use the syringe to annoy another student!

SYRINGE Things that annoy other students: –Blowing the syringe in their face or anywhere for that matter –Taking someone elses syringe without asking

MATERIALS You have the following materials –Syringe –Tubing –Binder clip

SYRINGE See if you can answer these questions: –What happens to the air in the syringe when you push and pull on the plunger? –What can air do?

3 3 Example: When you push the plunger down, the air in the syringe is pushed out the tube. Example: Does air have weight?

Air Observations When you clamp the tube closed and push the plunger down, what happens to the air? –The air is pushed into a smaller space. Is there more air, less air, or the same amount of air in the syringe when the air is pushed into a smaller space? –Same amount

Air Observations What happens when you let go of the plunger after pushing down? –The air pushes the plunger back up. What do you think happens to the air when it is pushed into a smaller space? What happens to push the plunger back out when you release the pressure on the plunger?

COMPRESSION When you push on the plunger, the air is forced into a smaller space. We say the air is compressed. The same amount of air is still in the syringe when it is compressed.

PRESSURE Compressed air pushes back with a force equal to the force compressing it. If the force on the plunger is released, the pressure in the compressed air will push the plunger out. The compressed air pushes back, and the push is called pressure!

GAS IN A SYRINGE GAS IN A SYRINGE

AIR Everything is made out of atoms and molecules, including air. The molecules in gases are free to move around throughout the volume of gas. There is a lot of space between the molecules in gases.

AIR When a volume of gas is compressed into a smaller space, the molecules are pushed closer together. The number of molecules is the same; they are just closer together.

AIR Molecules compressed into a smaller space bump into one another more often, and this creates pressure. Pressure pushes in all directions, and if the force keeping the gas compressed is reduced, the gas will expand into a larger space and the molecules will get farther apart.

WORD BANK Compression- When air is forced into a smaller space. Pressure- compressed molecules pushing back with a force equal to the force that compressed it.

3 Let’s review our questions Example: Does air have weight?

Where’s the Air?

From Yesterday True or False: The syringe on the left has more air than the syringe on the right. Why or why not?

Questions Does air have weight (mass)? Where does air pressure come from? How does air push the syringe plunger out? Why is air pressure so strong?

Questions Does air have weight (mass)? – Balloon ClipBalloon Clip

Does air have mass? Every object and substance in the world is made of matter. Matter is the stuff that everything is made of. The amount of matter in an object is its mass. Mass is the measurement of the amount of matter in an object or a substance such as air. Mass is measured in grams.

Does air have mass? One way to confirm that something has mass is to weigh it. Weight is pull or force between Earth and the matter in an object or substance. Weight can vary slightly at different places on Earth and can vary greatly on different planets.

Does air have mass? In outer space, away from planets, objects become weightless, but their mass does not change. So let’s restate our question: –Does air have mass? –Is there any matter in a volume of air?

EXPERIMENT What experiment can we conduct to find out if air has mass? Materials available: –Round balloons –Clear straws –String –Paper clips –Tape

SHARE RESULTS What experiment did you perform? What were your conclusions, what did you learn?

EXAMPLE EXPERIMENT

ANALYZE RESULTS Blowing up a balloon requires forcing air against a resistive force of rubber. The elasticity of the rubber puts pressure on the air in the balloon. The air in the balloon is compressed.

ANALYZE RESULTS Compression pushes the molecules closer together. There is more air in the volume defined by the balloon than there is in an equal volume of uncompressed air outside the balloon.

ANALYZE RESULTS Two balloons full of compressed air are balanced. When air is let out of one of the balloons, the air is no longer compressed.

ANALYZE RESULTS The balance tips down, and the balloon full of compressed air sinks because it has more mass than the deflated balloon with very little air. Air has mass, thus air is matter!Air has mass, thus air is matter!

READING: “What’s in the Air” page 6

WORD BANK Matter- the stuff everything is made of. Mass- the amount of matter in an object measured in grams.