Bad eggs float because their internal composition changes over time, making them less dense than fresh eggs. This is primarily due to the increase of gas inside the egg, and a corresponding decrease in water content, causing the egg to become buoyant.
The Science Behind Egg Buoyancy
Here's a detailed breakdown of why bad eggs float:
Density and Buoyancy
- Density is a measure of how much mass is packed into a given volume.
- Buoyancy is the tendency of an object to float in a fluid (like water). An object will float if it's less dense than the surrounding fluid.
How Eggs Change Over Time
- Gas Buildup: As an egg ages, gases are produced inside, primarily due to bacterial decomposition. The reference states, "as the egg gets older it ends up with more gas inside...".
- Water Loss: Simultaneously, water evaporates through the eggshell, reducing the overall weight.
- Density Decrease: The gas that is produced is lighter than the water that is lost. As the reference states, "and the gas is lighter than the water". Thus, the egg's overall density decreases, as gas is less dense than water.
- Floating Effect: When an egg's density becomes lower than that of water, it will float.
Fresh vs. Bad Egg
| Feature | Fresh Egg | Bad Egg |
|---|---|---|
| Internal Gas | Minimal | Increased |
| Water Content | Higher | Lower |
| Density | Higher (more dense than water) | Lower (less dense than water) |
| Buoyancy | Sinks in water | Floats in water |
The Float Test: A Practical Method
The "float test" is a simple way to check egg freshness:
- Fresh eggs sink: Due to their higher density, fresh eggs will usually sink to the bottom of a glass of water.
- Stale/bad eggs float: Eggs that float are typically older and have accumulated enough internal gas to reduce their density, indicating they are not fresh.
Conclusion
In summary, the primary reason bad eggs float is because they lose water and accumulate gases, reducing their overall density to a point where they become less dense than water, causing them to float.
