Atmospheric pressure refers
to the weight of the air exerting a force or pressure on an object.
All things, living and non-living, are subjected to this pressure.
Students do not usually think of themselves as being on the surface of
the Earth with tons and tons of air on them. They assume that they
could not possibly be able to walk around with such pressures placed upon
An instrument called a barometer
measures the atmospheric pressure. An analog to a barometer is a handboiler
or love meter. Let one of the students hold the meter in their hand.
The class should observe what happens and try to figure out what causes
the liquid to boil. Many will assume that the heat of the hand boils
the liquid, but it doesn't. The liquid inside the glass chamber
is usually methyl alcohol or another liquid that has a low vaporization
rate. The heat of the hand starts to vaporize the liquid, that in
turn changes the pressure inside the chamber and forces the liquid up.
The air in the chamber then is forced up after the liquid is up and it
appears like it is boiling.
Air has weight and hence creates
pressure. The weight pulls down on us and creates a pressure.
The pressure is equal in all directions. In this activity the students
will use different bubble makers to discover that the reason bubbles are
spheres, is because the pressure acts on their surface equally, forming
a sphere. In space where is there is not air pressure, the pressure is
still equal so you will still get spherical bubbles.
- Use the Tour of Bubbles to watch the bubbles move
upward. Notice at the beginning of the bubble, they are more oblate
(flattened). As the bubble moves upward it becomes spherical. This
is because the pressure is equal when it is spherical and unequal when
it is oblate.
- Use the bubble trumpet or other bubble makers to have
children look at the shape of the bubbles that leave the trumpet.
- Give groups of students 4 pieces of stiff wire (no more
than 10 cm long). Direct them to make a shape of a circle,
triangle, and square. The fourth shape can be one of their choice.
- Students should do 4 trials of each wand and record
their information. Scientific experiments always need more than one
experiment to prove something. All the bubbles should be spherical.
- Students should test their bubble makers using bubble
solution. Below are some solutions that you can use. Note:
Dawn (or other soap with high glycerine content) can be substituted for