Tuesday, March 30, 2010

Science Experiment: Why No Flood?

Today we did our first experiment from this great book!


Why No Flood?

You will need:

  • a piece of cardboard or large index card
  • glass of water

What to do:

Place the cardboard over the drinking glass which you have filled to the brim with water.IMG_0731 IMG_0732

Make sure no air bubbles enter the glass as you hold the cardboard against it. IMG_0733 Then turn the glass upside down over a sink or basin. Take away the hand holding the cardboard.

What happens:

The cardboard stays in place- and the water stays in the glass.IMG_0734IMG_0736


The pressure of the air outside the glass is greater than the pressure of the water inside. It is the air pressure that keeps the water in the glass.

My notes:

  • I practiced this trick a few times during the kids naps so i knew what i was doing beforehand :) (that’s also why the cardboard is wet in some of the pics, not because the water was leaking from the cup)
  • I somewhat ‘slid’ the cardboard over the cup to let less air in than if i had just laid it over the top.
  • When explaining this trick to connor and bri (mostly connor), i focused on explaining about the air- that because there was no air, the cup was suctioned to the cardboard. But once air got inside, the cup let go.
  • This trick worked almost everytime. However depending on how much air slipped in, some times the cup lasted longer than other times. So make sure you try this experiment over a sink as the cup will drop at some point and water will splash out! Connor got a kick out of this.

Let me know if you try this out! It was fun and easy :)


  1. Oh, I remember doing this when I was a kid! How neat! What a great idea for a quick and easy experiment!

  2. I did that with my oldest a couple of weeks ago. Nice and simple.

    As for your question about the erasers and the scanner...Yes! That's exactly what I did. I lined them up on my scanner and laid a sheet of white paper over them. Worked great.

  3. Such a cool experiment. I have an Easter basket and a couple awards for you on my blog.

  4. I remember doing this as a kid too! I think my kids will LOVE this experiment. I'll definitely practice too!

  5. I love seeing what you and your kids are up to. Cool Stuff

  6. Great classic experiment. I love your discussion at the end telling of possible pitfalls. Great post!


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