This document discusses air pressure and how it relates to various phenomena: 1) Air pressure is higher outside an inverted cup filled with water than inside, allowing the cup to hold water without leaking. 2) Sucking on a straw creates lower pressure inside, allowing outside air pressure to push liquid up the straw. A leaky straw cannot maintain the lower pressure. 3) Plugging a hole in a container prevents air from entering and equalizing pressure, allowing outside air pressure to push liquid from inside. 4) Boiling water in a sealed can removes air, lowering inside pressure so outside pressure crushes the can upon cooling.

1. PRESSURE
force of air pressing down
Less air particles- Low air More air particles- High air
pressure pressure

2. High to Low
Pressure
(Many to Less)
How do you
change the
pressure?

4. Inverted Cup
When cup is completely
cardboard filled with water, no air is
left in cup, thus no air
pressure. The inverted cup
can therefore hold water
up because the air
pressure is working against
the underside of the cup.
Air Pressure
There is higher air pressure outside pushing upward than
the inside of cup pushing downward.

5. Straw Drinking Race
The higher pressure in
outside air pushes the
liquid up the straw in our
mouth
The student with the leaky
straw cannot create a
Sucking creates a vacuum above the
partial vacuum or a liquid, so the liquid is not
lower pressure in
pushed up.
straw above the liquid
that we drink

6. Stop the Leak
By plugging one of the holes, the air
inside stays the same because
outside air is prevented from coming
Air cannot go into the hole. The higher water
in volume inside causes a decrease in
pressure. Thus, outside air pressure
(which is greater) pushes against the
water and prevents it from flowing
out.
Liquid
cannot
Air pressure outside of can is greater
flow out than air pressure inside.

7. Collapsing Can
Before heating, the can was filled with water and air.
By boiling the water, the liquid changed into water vapor
 The water vapor or steam pushed the air that was inside, out of the can.
 In closing off the can, air is prevented from going back to the can.
 Cooling (water in basin) condenses water vapor back to water. All the
vapor which took up space inside the can turned into a few drops of
water, which take up less space.
 Pressure inside can drops allowing outside air pressure to push on the can and
crush it.