About this Daily Classroom Special
Weigh Air was written by Ed Clement, former Teachers Network web
mentor and a teacher in the Chicago public school system for twenty six
kids in 3rd through 12th grades.
- Build science skills .
- Show kids that air has weight.
YOUR STUDENTS WILL SEE THAT AIR HAS WEIGHT
Air planes and gliders depend on the differences in air pressure created by their wings to create lift and fly. In order for there to be air pressure air must have weight. That is a very hard principal for children to perceive because air is hard to measure especially with the tools found in a typical inner city grammar school like mine. After several unsuccessful attempts I was finally able to demonstrate that air has weight. The steps below show how I weigh air in my classroom.
- Gain access to a sensitive scale. (I use a balance beam scale, like the one
pictured above, which I borrow from the nurse's office. It is sensitive enough to
measure the .5 lb
difference in weight that is needed to measure the air. This
type of scale also gives good visual cues to weight when
the needle moves as the weight differences occur. Any scale
that is relatively sensitive and can handle 100 pounds of weight will do.
- Get a SUV tire and fill it with air. (I found that a car tire
will not work. Most scales available to me were not sensitive
enough to measure the amount of air they hold. I borrowed a
Jeep tire from a dealer near the school. They were very
willing to loan me a tire any time I do the lesson on air
- After the discussion of air pressure during the Styrofoam glider unit described on this web site, I roll the tire onto the
scale and set the weights. I then remove the valve core and
release the air from the tire. As the air first whistles then
whooshes out the scale pointer moves showing that the loss of
air reduces the weight of the tire. A simple recalibrating of
the scale weights and a little math will show the actual
weight of the air that was released from the tire.
- I usually repeat the experiment a couple of times. This
requires bringing a small air pump and tire air pressure gage,
which I also borrow from the Jeep dealer, to fill the tire
before releasing the air again. (I think it is important to
note that the dramatic whistling and whooshing of the
released air and the obvious movement of the scale pointer
seems to provide a lasting impression on my students.)