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Is Air Really There?

If you go to your closet and
take all your stuff out, is it
really empty?
If you uncap a bottle of soda and
pour its contents in a glass, is the
bottle really empty?
If you open a can of food and
pour it into a bowl, is the can
really empty?
The answer to all of these questions
is “no”, because air is still inside the
containers. As soon as you take the
stuff out of your closet, pour your
soda in a glass, or pour the food
out of the can, air flows inside to
fill the “empty” space.
If you don’t believe it, ask an
adult to help you try this…
1. Empty a small bottle of water
or soda.
2. Turn the bottle upside down, so
that the opening points down,
and push it into a large bucket
or sink filled with water.
3. Slowly flip the bottle right side up
again while keeping it underwater.
What happened? Did you see
bubbles? What was in the bubbles?
Did the bottle stay empty?
When you turned the bottle right
side up again, the air that was
trapped inside the bottle escaped as
bubbles. The water that was inside
the bucket or sink flowed into the
bottle until it was full. So the bottle
was never really “empty”.
A space that is truly empty is called
a vacuum. On Earth, we don’t have
any truly empty spaces, because
air––or something else—is
everywhere. But we can remove
some of the air from a place
temporarily. One way to do this
is with a vacuum cleaner.
A compartment in the middle of a
vacuum cleaner catches dust and
dirt in a bag. A small hole for
attaching a hose is at one end of
the compartment, and a fan is at
the other. Most vacuum cleaners
also have other parts, like beater
brushes and nozzles, but inside they
are all about the same. They have a
dust compartment (which may have
a bag in it), a hose (with a nozzle
on the end), and a fan. See the
illustration below.
When you turn on a vacuum cleaner,
the fan inside starts to spin very
quickly. The fan is positioned so
that it pulls air out of the dust
compartment and blows it out the
back of the vacuum cleaner. As a
result, air must rush through the
hose at the other end to refill the
dust canister. Because the fan blows
the air out of the vacuum cleaner
faster than the air can race through
the hose to refill it, a “partial
vacuum” occurs. The result is that
the vacuum cleaner sucks air and
dust through the hose, helping us
clean our floors and carpets.

http://portal.acs.org/portal/PublicWebSite/education/whatischemistry/scienceforkids/articles/CSTA_015161