Education Technology

Summer of STEM: Egg in a Bottle

Posted 06/27/2018 by Erick Archer

How can you get a hard-boiled egg inside of a milk bottle without pushing it?

What you’ll need:
  • Milk bottle or equivalent with an opening diameter of about 2.5” to 3”
  • Small to medium hard-boiled egg
  • Cooking oil
  • Matches or a lighter
  • 3” x 3” piece of paper
What to do:
  • Coat the opening of the bottle with cooking oil to decrease friction.
  • Loosely roll the piece of paper and light it with the match or lighter, being careful not to burn yourself.
  • Drop the lit paper into the bottle and quickly but gently, place the egg onto the bottle opening on one end or the other.
  • Watch the egg get sucked into the bottle.
How it works:
  • The burning paper quickly heats the air inside the bottle, causing an expansion of air inside the bottle.
  • That warm air pushes out through the top of the bottle and past the egg.
  • Because the fire burns up the oxygen inside the bottle quickly, and the egg is acting to stop any incoming air by acting as a seal, the air pressure inside the bottle quickly becomes less than the air pressure outside the bottle and above the egg.
  • The difference in air pressure between the inside and outside causes the egg to get pushed into the bottle!
  • Notice the paper probably didn’t burn all the way. That is because the rate of incoming air was too small (due to the egg blocking the opening), and the fire went out since there was no more oxygen to burn inside the bottle.
  • To remove the egg without destroying it or the bottle, invert the bottle so you can get the remaining paper out. Then, invert it fully so the egg is in the opening. Put your mouth on the opening and blow hard while keeping the bottle inverted. After a quick puff, remove your mouth to allow the egg to escape … otherwise you will be eating egg.☹️

Below, see a video of this experiment and others in action: