THE POWER OF AIR PRESSURE

You Will Need:

• An empty gallon milk or water jug, with lid.

• Water

• 2 quart sauce pan

• Stove

• Pot holder

• Funnel

• Large pot, bucket, or large mixing bowl

• Ice, at least 3 trays worth

GETTING READY

1. Remove ice from ice trays, and put into the pot, bucket or mixing bowl.

2. Open the milk jug, and set it on the counter.  Keep the lid nearby, as you will need it quickly.  Place the funnel into the mouth of the milk jug.

3. Put one cup of water into the sacepan.  Place on stove, and bring to full boil.

PERFORMING THE EXPERIMENT

1. Carefully pour the boiling water into the milk jug.  Allow to sit for ten seconds.  Cap the jug tightly.

2. Place the milk jug into the ice.  Nestle it down inside, so that the ice is coming up the sides of the jug as far as possible.

3. Watch what happens to the milk jug.

EXPLAINING HOW IT WORKS

All materials expand (get bigger) when they are heated, and contract (get smaller) when they are cooled.  As the water heats up, and turns into water vapor, or steam, it takes up much more room than it would as liquid water.  

When you put the hot water into the milk jug, the steam rising off of the water filled the space inside the milk jug.  Because the water vapor, and air are at a higher temperature, they expand rapidly, filling the entire area inside the milk jug.  By capping the jug, you keep the expanded air inside the jug.  

The ice outside the milk jug rapidly cools the water and air inside the jug, causing the molecules to move slower, and closer together.  This decreases the air pressure inside the jug, while the air pressure outside the jug remains the same.  The now greater air pressure outside the jug presses in on the sides of it, causing it to crush.