Sometimes you just have to force a hard boiled into a bottle, right? No? Well, this simple demonstration will amaze and astound your friends by showing how differences in air pressure can affect things.
Safety Warning: You will be using matches so make sure your parents are helping out.
- A glass container with a lid a bit smaller than an egg (I used a Starbuck’s Iced Coffee bottle)
- a couple of peeled hard boiled eggs
- Empty, clean, and dry out your glass bottle. It is important that the bottle lid is just small enough to stop a hard-boiled egg from going in it. Too small and this won’t work as well
- Fold a small piece of paper (approximately 1” x 6”) in half
- Light the end of the paper and drop it into the bottle
- Make sure the fire is still going when you put the egg on top of the glass bottle
Several things happen as soon as you put the egg on top of the bottle. You should notice this jump up and down a bit. What is going on here?
Hot air expands, and so the hot air is pushing out of the bottle, but the egg is in the way, forming a nice seal. To get out, the air makes the egg jump.
Next, the fire goes out when the oxygen is used up (oxygen is needed for things to burn). When this happens, the air cools down again. It does the opposite of expanding, and now it shrinks! As it shrinks, it forms low pressure, or a “vacuum,” because now there is less air in the bottle than before you put the egg on it. (Remember the air pushing out?)
Nature does not like a vacuum, so it tried to balance out the low pressure. As a rule, high pressure goes to low pressure, and the egg just got in the way. The high pressure pushes the egg into the bottle!
Now, how do you get the egg out? Depending on the bottle, the following trick might work: Hold the bottle upside down and blow air into it past the egg. The high pressure you push into the bottle will want to push out (much like a balloon), and the egg will slowly push out. If that fails, just give it a few quick shakes. Don’t expect the egg to stay in one piece, though!
What can you do to change the results of this experiment? Different bottle openings? A strong plastic bottle instead of glass? Just remember to be careful with the matches, and have a parent observing this.
I hope you enjoyed this simple experiment. If you have more questions about this, or need tips about science fair ideas around this topic (or others), contact the author.
Steve Davala is a middle school science teacher who likes to write and work with Photoshop. He’s got two kids of his own and subjects them to these science activities as guinea pigs.