Here's an amazing way to get a hard-boiled egg into a bottle, even though the mouth of the bottle is smaller than the egg! What's more, you don't even need to touch the egg to get it to go in!
Glass bottle with a long, narrow neck
Put the empty bottle on a table.
Peel the boiled egg.
Light a match and drop it into the bottle. Repeat about three or four times.
Quickly put the egg over the mouth of the bottle.
So how does this squishy-but-solid egg get mysteriously pushed inside the bottle? The answer is all about air pressure. When you first set the egg on the bottle, the air pressure inside the bottle matched the air pressure outside, so nothing happened. When you dropped the burning paper into the bottle, it caused the air inside to heat up and expand rapidly. That expanding air pushed the egg aside and escaped from the bottle; that's why you saw the egg vibrating. When the fire consumed all the oxygen inside the bottle, the flame went out and the remaining air in the bottle cooled down. Cool air takes up less space, exerting less pressure inside the bottle. (The egg acted as a seal to prevent outside air from getting in to fill the extra space.) The result was an unbalanced force—the force of the air pushing on the egg from outside the bottle was greater than the force of the air pushing up on it from inside the bottle. Voila - the egg was pushed into the bottle!
How do you get the egg out again? You need to increase the pressure inside the bottle. Turn the bottle upside down and tilt it until the small end of the egg is sitting in the mouth. Now put your mouth close to the bottle and blow, forcing more air into the bottle and raising the pressure inside. When you take your mouth away, the egg should pop out - just be careful it doesn't hit you in the face!
If you've taken photographs of your activity you can send them to this email address Liam.Gillespie@gilmourjuniors.com