Learn about the relation of temperature and pressure as you watch an egg get sucked into a bottle. This project requires adult supervision.
>> Watch our video demonstration below, and then try it yourself!
First, the science behind a hard-boiled egg: Egg whites are made of water and proteins. Proteins are made of long chains of amino acids, but in an egg the chains are clumped tightly together in individual spheres. (These are called "globular proteins.") When the egg is heated, the proteins and water molecules begin to move faster. As they move and collide with each other, the individual protein chains start to "unravel," eventually bonding loosely with other protein chains, forming a network of protein with water trapped inside. The consistency has changed from runny egg white to a soft solid!
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!