The Leaping Egg

What do you think a build-up of air pressure can do to an egg? Do you think an egg can jump like a frog – from one glass to another? There’s only one way to find out…

Question: Is there a way to make an egg jump?

Materials:

  • 2 identical wine glasses (make sure to get permission from a parent!)
  • 1 egg at room temperature
  • Needle
  • Tape (optional)
  • Adult helper

 

Procedure:

1. Have adult helper (or permission from adult helper) pierce the egg shell at both ends with the needle. Scramble the yolk inside using the needle. (Create a slightly bigger hole at the large end of egg, using the needle.)
2. Blow through one hole of the egg (smaller end) over the sink until all the egg is blown out. You may need your adult helper for this!
3. Place the two wine glasses about 2-3 cm apart on a table and secure to the table with tape (if you are really careful and can hold them down firmly, you won’t need to tape them down).
4. Put the empty egg in one of the glasses.
5. Blow a short and hard puff obliquely into the far side of the wine glass that holds the egg and watch the egg leap! (It may take a few practice blows to make it leap successfully. If you can’t seem to get it to leap, ask your adult helper to try.)

What Happened – and Why?

What makes the egg jump out of the first glass? Why would the egg not go toward the one that blows? What does flowing air create? How far apart can we place the second glass in order for this one still to catch the leaping egg or ball? What would happen if we blew on the near side of the egg?

Blowing obliquely into the far side of the glass builds the pressure on that side. This pushes the egg out of the glass and the flowing air above both glasses guides the egg towards the second glass, because the flowing air actually creates a lower pressure. The harder you blow, the farther the second glass can be placed to catch the leaping egg. (Warning: do not try this activity with a raw egg that has not been blown empty!)

Source: Adapted from Science Inquiry Enterprises; 1998