High And Dry Demonstration
* A Cup
* A Pot
* A crumpled up piece of paper
* Be careful not to spill water on the floor.
Students will expect that
the crumpled up paper to be wet when the cup is pulled out of the pot of water.
1. Crumple up a piece of paper and put it into the bottom of a cup.
2. Fill a larger container about ¾ full with water.
3. Turn the cup upside down and slowly push it into the larger container.
Slowly pull the cup out of the container of water.
Examine the piece of crumpled up paper.
What did you expect to have happen?
Why do you think happened?
3. Do you think you would have the same results if other liquids such as vegetable oil were used?
the paper did not get wet is this: The air remaining in the cup pushed down on the water in the container. The
push of the air on the water kept the water from moving into
the cup and getting the paper wet. This is a great visual demonstration of how great the pressure is that air exerts on other objects. Air pressure is a
tough concept to grasp because air is not something that can be seen. It
appear to be there, so how could it actually push anything out of the way? Just because something is invisible does not mean that it does not exist. This
demonstration helps prove that air exists and that it can
apply pressure on another object.