An Experiment about Air Pressure

Laura has been learning about air this week.  Today we had an experiment on air pressure.  The experiment is simple, but when things don't work it can get kind of funny.  There was a reason we were told in the instructions to do the experiment over a sink or a bucket or to do it outside.

First we filled a cup with water.

Then we wet down a piece of cardboard.

We placed the wet cardboard over the top of the cup.

Then we tipped the cup over.  Air pressure is supposed to hold the cardboard in place.  However, we learned that the cardboard we were using wasn't heavy duty enough, and our cup wasn't sealing to the cardboard at all.

SPLAT!!! The water flooded out into the sink.  We couldn't get enough air pressure to for the experiment to work.

We ended up having to start the experiment over.

We used a different cup.  It had a different rim that would seal better with the air pressure.

We picked a heavier cardboard.  We wet it and put it on top of the cup of water.  Carefully we flipped the cup over and...

This time it was a success.