Lesson 3

Materials: large plastic containers, push pins and water source.
Children use play, observation, metaphors and a puzzle to explore the idea of pressure.
Using simulations and videos, students reinforce their understanding
of the behavior of particles in solids, liquids and gases.

What did you do last time?

condensation

state

evaporate

freeze

boil

melt

PRINT the word next
to the image on the next slide.

Let’s explore water, a liquid.

Punch
a second hole
about 3 inches
(7 cm) above the
first.

water

Punch the lowest hole
at least 1 inch (2.5 cm)
from the bottom.

You will need:

Punch
two holes
in the jug.

push pin

one gallon or 4
liter plastic jug

What do you predict?

shoot out,

What will happen when you
fill the milk carton with water?

flow smoothly,

dribble and burp?

Will it:

Problems?

Things will not work if:
1. The holes are not the same size
     or not punched completely through.
2. The bottom hole is not punched
     on the flat edge of the jug.
3. The bottle cap is left ON the jug.
4. The jug is not lifted off the ground,
     so the result is not obvious.

Fill the milk jug with water.
Do this either outside or in your bathtub.
Lift the jug off the ground to see clearly.

What happens?

NO CAP!

You should see this.

Did the water come out the bottom
and top holes in the same way?

There is more PRESSURE on the water
in the bottom of the carton
from all the water above it,
so it squirts out straighter and farther.

PRESSURE!

WHY does the lower stream
shoot out the farthest?

To understand PRESSURE, ask yourself this question:

You are "squished" more
if you are on the bottom.

The children on
the bottom are under
more PRESSURE
than the child on the top.

Where would you rather be --
on the TOP or
on the BOTTOM?
Why?

PRESSURE

So it is with the water.

The water in the bottom of the bottle
is under greater PRESSURE from above.

So the water on the bottom
is squeezed harder and shoots out farther.

There are 4 water fountains in a row.

The fountains are all connected to one main water line.

Does the main water line come in
at A
or B
or C

The water fountains at each end
do not deliver much water
when the two in the middle
are in use.

Liquids have pressure.

Gases exert pressure, too!

You put pressure
on the sides of a balloon -

when you fill it up with a gas.

Air molecules PUSH
on the sides of a balloon...

as you blow it up.