Materials Needed

• one jar
• glass plate large enough to cover mouth of jar

Procedures

1. Fill the jar with water all the way to the brim.
2. Put the glass plate on top of the jar. Make sure that no air is trapped between jar and glass plate.
3. Quickly turn the jar upside down. (Hint: It might take a few times to get this right, so this test should be performed over a sink area.)

What Happened?

You may think that atmospheric pressure is just a downward force. It’s not. It is a force acting in all directions. That is why the plate stayed attached to the jar.