You’ll need

  • A hard-boiled egg (or an egg-sized water balloon)
  • A glass bottle with an opening slightly smaller than the egg (a 1 l juice bottle works well)
  • Margarine
  • Hot water (recently boiled is best!)
  • A sink or bowl (for the used water)
  • An oven mitt

 

What to do

Warning!

Hot water can burn your skin, so please be careful.

  1. Gather your materials on a flat surface.
  2. Peel the hard-boiled egg, or fill the water balloon with cool tap water to the size of an egg and tie it off.
  3. Use the margarine to grease the opening of the glass bottle.
  4. Fill the bottle with hot water and wait 10 to 15 seconds.
  5. Put on the oven mitt and empty the bottle by pouring the hot water into the sink or bowl. Stand the empty bottle on a flat surface and place the egg or water balloon on the bottle opening.
  6. Watch what happens!  It might be a little slow, but be patient!
  7. To get the egg out of the bottle, grease the opening of the bottle with margarine again. Make sure there is margarine well inside the opening.
  8. Tip the bottle upside down and shake it gently until the egg is sitting in the mouth of the bottle, sealing the opening.
  9. Now prepare to get egg on your face! Hold the bottle upside down above your head and blow sharply through the mouth of the bottle at the egg. This can take some practice to get right.

Questions to ask

Try the experiment with cold water instead of hot water. Does it work?

What did the hot water do to the air inside the bottle?

What did blowing in the bottle do to the air inside the bottle?

What's happening

As air warms up, it expands (or increases). As air cools, it contracts (or gets smaller).

The hot water in the bottle heats the glass. After the water is poured out, the glass stays warm and warms the air inside the bottle. This makes the air expand so that some air escapes through the neck of the bottle. Sealing the bottle with the egg traps the warm air inside the bottle. As the warm air cools, the pressure in the bottle goes down. Now, the bottom of the egg is being pushed up by the low-pressure air in the bottle. The top is being pushed down by the higher-pressure air outside. The high-pressure air outside pushes harder. This imbalance forces the egg into the bottle.

To get the egg out of the bottle, the air pressure in the bottle needs to be higher than the air pressure outside the bottle. When you blow inside the bottle, you increase the amount of air inside the bottle, creating higher pressure. The higher air pressure inside the bottle then forces the egg out of the bottle, sometimes with messy results!