Physics Grade 10 Gas laws Isoprocesses Egg in the bottle

Egg in the bottle experiment

What You Need:

• Eggs
• Saucepan and stove
• Wide-mouth glass drink bottle (such as a Starbucks Frappuccino bottle - the mouth needs to be a little smaller than the egg. We used a large egg wih the Starbucks bottle, but with other bottles you might need smaller eggs. )
• Vegetable oil
• Matches
• Strips of paper folded a couple times length-wise (slightly shorter than the bottle)

What You Do:

1. Place the eggs in a saucepan and add enough water so that the eggs are covered by about an inch. Let the water boil for 5 minutes, then remove the pan from the heat and cover it. Let it sit for 25 minutes, then remove the eggs and dip them in cold water.
2. Use a paper towel to coat the inside edge of the bottle mouth with a little bit of vegetable oil for lubrication.
3. Peel one of the eggs, then dip it in water and set it with the small end down in the mouth of the glass bottle. It should be slightly larger than the mouth of the bottle, so it doesn't fit inside.
4. Use a match to light the end of a strip of paper on fire. Lift the egg off the bottle, drop the paper inside with the flame down, and quickly replace the egg. Watch the egg wiggle a little in the bottle mouth, and then get sucked inside!

What Happened:

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!