Life under Pressure: Experiments with Air Pressure

Did you know that you are under pressure every day? I am not talking about pressure from schoolwork or chores. I am speaking of the air pressure that pushes all around you.

We need air to live. Without air we couldn't breathe! But air is actually composed of many gases, only one of which is oxygen. Even though we can't see them, the molecules of gases move the air around continuously. A simple definition of air pressure is the push that air has upon anything it touches. This push comes from the molecules in the air moving around and bumping into everything.

The definition sounds simple enough, but do you really understand how much force air has from just reading about it? You do not usually feel air pressure because you have gotten used to it. Observing air pressure through the experiments below will give you a much better understanding.

Experiment 1: The Book Blast 

When air is compressed (pressed together), it has a lot of strength. Try the experiment below to experience how air pressure can move items.

Items Needed:  

• 3 books
• 1 medium to large airtight bag

Directions: 

First, place the books on top of the bag with its opening hanging slightly over the edge of the table. Gather the bag opening together, leaving only a very small space open for air. Next, blow into the bag as though you are blowing into a balloon. Depending on the size of the bag, you may have to blow several times. Take your time, but close the opening all the way if you need to take a break so you do not lose the air you've already blown in. What happens to the books? They should lift off the table.

Later, ask a friend or family member if they can move the books by blowing at them. Let them try. Then you can show them how you can make it happen.

Experiment 2: Marshmallow Man 

When an object is solid, air pressure pushes on it—but you may not see the effects of it. If an object is squishy because it has a lot of air inside it, you can see the effects of air pressure much more easily. Just watch the Marshmallow Man as you change the air pressure around him.

Items Needed: 

• 1 straw
• Mirror
• Modeling clay
• 1 nail
• Hammer
• 1 clear glass jar with metal lid
• 1 or 2 large marshmallows
• Marker

Directions: 

First, draw a face on each flat side of the large marshmallow. Second, with adult supervision, use the hammer and nail to put a hole in the middle of the jar's metal lid. With that done, carefully slide the straw into the hole. Make some of the modeling clay into an airtight ring around the straw where it goes into the lid. Putting clay on both sides of the lid where the straw goes in will help hold the straw in place as well. Place your Marshmallow Man inside the jar and screw the lid into place.

Holding the mirror so that you can see the Marshmallow Man's face, suck the air out of the jar with the straw. Watch him carefully. When you can get no more air from the jar, release the straw opening and allow air back into the jar. What is the effect of the differing air pressure on your Marshmallow Man? The air inside the marshmallow is affected by the change in air pressure in the jar. Isn't that a fun way to make funny faces!

Experiment 3: Karate Chop Action 

Make sure you use a cheap yardstick for this experiment! Ideally, it will be one you got for free at the local fair or hardware shop. This experiment is a lot of fun, but it does have a little destructive twist.

Items Needed: 

• Cheap wooden yardstick
• Newspaper

Directions: 

First, place the wooden yardstick on the table, letting it hang about halfway off the edge. Give the yardstick a great big karate chop on a spot hanging off. What happens?

Next, place the yardstick on the table in the same position, but place a full, unfolded sheet of newspaper over the section on the table. Give the yardstick another great big karate chop. What happens this time?

Why do you think this happened? Although the sheet of newspaper does not weigh very much, it has a larger amount of area for the air pressure to push down. Therefore, it holds the end of the yardstick down as if a heavy object were placed on top of it.

Air pressure really is all around us, and it is amazingly strong! 

*This article published on August 11, 2010.

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Melissa Pinkley

enjoys life with her husband, Wes. They learn a lot from their four children: Ben, Micah, Levi and Abigail. Homeschooling goes on 24/7 for the whole Pinkley family. They have been homeschooling for 10+ years.  The Lord is gracious and continues to help them follow Him. 

This article was originally published in the May/Jun 2010 issue of Home School Enrichment Magazine. Sign up now to receive a FREE sample copy! Just click here: http://homeschoolenrichment.com/magazine/request-sample-issue.html