Why do egg shells break when you boil them?

Egg shells don't actually break when you boil them. The cracking you hear is actually caused by the expansion of the air inside the egg. Here's why:

* Air Pocket: There's a small air pocket at the wider end of an egg. This pocket expands as the egg heats up, creating pressure inside the shell.

* Pressure Build-up: As the temperature of the water increases, the air inside the egg expands. The pressure inside the shell can get quite high.

* Shell Thinning: While the shell is quite strong, it's not perfectly rigid. The heat of the water can weaken the shell slightly, making it more susceptible to cracking.

* The Cracking Sound: The pressure inside the egg eventually overcomes the strength of the shell, causing it to crack. This is what you hear as a "cracking" sound.

Important Note: If the egg cracks during boiling, it's not necessarily ruined. You can usually still eat the egg, although it might be a bit messy!

Here are some tips to reduce the chance of eggs cracking while boiling:

* Start with Cold Water: This allows the egg to heat up gradually and prevents rapid pressure changes.

* Add Salt to the Water: Adding salt to the water raises the boiling point, making it less likely for the air to expand rapidly.

* Don't Overcook: Boil the eggs for the recommended time only. Overcooking makes the eggs harder to peel and more likely to crack.

* Cool Down Quickly: After boiling, immediately plunge the eggs into cold water to stop the cooking process and prevent further pressure build-up.