Recommended Age Groups: Elementary School
Need ample elbow room so everyone can see the experiment.
Do not light matches and do this experiment alone! Fire is dangerous!
Be very careful when you use matches and light the piece of napkin or piece of paper and drop it in the bottle. Be sure you know the safety tips for lighting matches and handling them. You may want to do this experiment as a demonstration and have an adult handle the matches.
Share questions and ideas including:
What is air?
Share ideas and experiences with "air." Come up with some points like we cannot see, taste, or smell air. Air is all around us. We need air to survive and live.
What is air pressure?
Air is constantly pressing, forcing, moving and tugging on things around it.
What happens when air is heated up?
When air becomes warm, it expands and takes up more space. This, in turn, causes pressure.
Today, we will do an experiment with an egg and a bottle that will help us better understand air and air pressure.
Crumple up the piece of paper or napkin.
Very carefully, light a match and touch it to the paper or napkin..
Drop the lit piece of napkin or paper in the bottle..
Quckly put the egg on the top of the mouth of the bottle with its narrow end pointing down.
Carefully observe what happens. Does the egg drop into the bottle? What happens to the lit piece of paper or napkin? Why do you think the egg got sucked down into the bottle?.
To get the egg back out of the bottle, first you have to rinse the bottle out to remove the burnt paper or tissue. Tip the bottle on its side and jiggle it until the egg falls near the mouth of the bottle. Hold the bottle so the egg stays near the mouth. Press your lips agains the mouth of the bottle and blow into it as hard as you can. Quickly, take the bottle away from your mouth. Tip the bottle upside down. Does the egg fall out? Why? Share ideas about pressure.
Share ideas aobut the guiding questions. Listen for evidence of understanding about air and air pressure.
What is air?
Air is the mix of gases in our atmosphere. Air is everywhere around us. It is tasteless, odorless, and invisible.
What is air pressure?
Air pressure is the pressing, forcing, and moving of air as it interacts with things around it.
What happens to air when it is heated?
When air gets warmer, it expands and takes up more space.
When and why does an egg drop down inside a bottle?
When we lit a fire in the bottle, the air in the bottle became much warmer. The air expanded as it got warmer and warmer and it was crowded in there for the air!
As the air inside the bottle began to cool off, it also shrank in size again. The air pressure inside of the bottle was reduced. So, the air pressure outside of the bottle and on top of the egg was greater than the air pressure inside the bottle. The air pressure from outside the bottle pressed and pushed the egg down the bottle.
What happened when we got the egg back out of the bottle?
When we blew and forced air back into the bottle, we increased the air pressure inside the bottle. So, the air was pushing and shoving the egg to get out of the bottle. We saw just the opposite thing happen with air pressure when we made the egg drop into the bottle. When there is air pressure, the air is shoving and pushing things around and in it.
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Last revised 23 Jan 05