Crush the Can Mini Lesson
Can heat be a source of energy? How powerful is heat?
Materials
1 Empty soda can per group
75 mL of water per group
Hot pot or hot plate
Tongs
Gloves
Ice
Thermometer.
Bucket
Plastic soda bottle
Balloon
Preparation
Use a hot pot to boil a small amount of water (50 mL per group). (Alternatively, pour
30-40 mL of water into the can and set it on the hot plate until it boils.)
Prepare a tank or tub with ice water. This should be large enough to submerge the
soda can.
Place a small rock in the bottle and place the balloon over the mouth of the bottle
with as little air in the balloon as possible. Place the bottle in the ice water.
What to Do
Show the students the empty soda can.
Ask if there is anything in it.
Remind them that even when a container is empty, it usually at least contains air.
Place the can with about 10 mL of water in the hot pot.
Ask the students what energy is.
Energy allows us to do things or to move. Heat is a form of energy.
For older students (4th, 5th grade) ask what is moving when things are hot.
Remind them that all matter is made of little particles called atoms and
molecules. They move faster when a material is hotter.
Ask if we can use heat energy to move something big
Allow the can several minutes to heat
Ask the students what they think is happening to the air as it gets warmer.
(It is expanding, but you don’t necessarily need to tell the students this. See if
they can figure it out from the demo).
Check the Temperature of the ice water and announce this to the students.
Using the tongs, quickly invert it into the ice water. Keep the mouth submerged. It
should not be necessary for the whole can to be submerged. As the air quickly cools,
the can should collapse.
Check the Temperature of the ice water again. It may have changed slightly, but
usually not more than a few degrees.
Where did the heat energy go?
Some of that energy was transformed into the mechanical energy of crushing
the can.
Move the bottle with the balloon over to the pot of boiling water. As the Air in the
bottle warms, the balloon should expand
Summary
Thermal (heat) energy is the motion of molecules. When molecules are cooled
rapidly they can cause other molecules to move faster (transfer heat) or cause the
pressure of a gas to drop rapidly, allowing normal air pressure to crush the can. In
reverse, as molecules absorb thermal energy, the try to push farther apart, causing a
gas to expand.