Reprinted from Connect
Vol.11 No.4, March/April, 1998
Focus on: Matter
Grade Level: 6-8
Grade Level: 3-5

Air Under Pressure

by Alicia Osborne

This is an activity that will wow young and old alike! We can all remember the party relays where each person runs with all their might to the empty chair and pops their balloon with the powerful plop of the ol' derriere! Where there is a balloon, there is a middle school person with a plop or a pin!

Now for the ultimate challenge: How much weight can you put on balloons and not pop them? (No pins or plopping allowed!)

Find two sturdy tables that are equal in size and height and can be lifted by a group of your students. The tables can be round, square or rectangular, as in the picture. Library tables are often appropriate.

Set the tables side by side with about three feet of working space between them. On the surface of one table, place 8-12 (depends on the size of the tables used) deflated round balloons equal distance apart around the edge of the table. Be sure to situate each balloon so the mouth is hanging off of the table.

Have one student in charge of each balloon so it stays properly situated. Have several other students carefully lift the second table and gently place it on top of the first table so they touch, top-to-top, and the mouth of the balloons are hanging off of the edge.

Each helping student is now on their knees ready to blow up their balloon but waiting for the signal from their teacher. The table lifting crew are scattered between the "air pump" crew, and at the teacher's signal they will lift the top table up about 5 or 6 cm and hold it until the other students inflate the balloons to this same height. The "air pumps" should quickly tie a knot in their balloon. Additional students on stand-by, may be called upon to help tie balloons. After all the balloons are tied, the lifting crew will let go of the top table.

Voila ! The top table is suspended on AIR! Well, kind of.... Anyway, just how much weight can we add and not pop those balloons? Sounds like time for some interclass competition to me! This fun illustration of Air Power is just the beginning of lots of class investigations. The following questions will help get you started. Remember when you let students climb aboard, be sure to review safety rules. Spotters are very important for each child.

How many kids will your system hold?

How many pounds?

How many kilograms?

How many balloons could you add or take away? Students can draw a plan.

What happens if you leave the table up for a few days, can the air escape?

Do you have to use round balloons?

How does the balloon circumference relate to the weight held?

How is the air in the balloons different from the air around the balloons?

What is the pressure in PSI?

What is the relationship between the surface area and pressure?

How would a temperature change affect the amount of weight the balloons could hold?

Regardless of the questions you choose to answer, the experience will be thought provoking and full of adventure! This is an activity no one forgets and is full of potential for math and science teachers.

As a science teacher, when conducting investigations into the states of matter, it's easy to teach about solids and liquids. However, gases are another matter. (No pun intended!) The hard-to-observe gases tend to be abstract for many learners. Air just happens to be the most accessible and comprehensible combination of gases there is! So, let's use it!

Balloons provide a common device with which most children have experience. Yet, many students and adults do not believe that balloons can be that strong. The strength of the balloon skin combined with the force of the compressed air, provide a demonstration of the presence of the gas and how it can behave under pressure.

Careful investigations can reveal answers to some of the questions in this article. As most teachers know, students will lead us to more ideas and then to the development of concepts, beyond what any of us alone can imagine. That is one delightful aspect of teaching with open-ended activities.

Alicia Osborne - Alicia Osborne has been a science educator for 22 years. She currently teaches at Pryor Public Schools, Pryor, Oklahoma. Alicia received a 1995 Presidential Award for Excellence in Math and Science
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