Making an egg float is a classic science demonstration that shows the principle of density. While an egg typically sinks in regular tap water, you can easily make it float by increasing the water's density. This is commonly achieved by adding salt.
Making an Egg Float: The Saltwater Method
The key to making an egg float is to make the water denser than the egg itself. Adding salt to water increases its density. The more salt you add, the denser the water becomes.
Understanding the Science: Density
Density is a measure of how much "stuff" (mass) is packed into a certain amount of space (volume). Think of it like this: if you have a box of feathers and the same size box of rocks, the box of rocks is much denser because rocks are heavier than feathers for the same amount of space.
An object will float if it is less dense than the fluid it is in. An egg is denser than plain water, so it sinks. By adding salt, you make the water denser. When the saltwater becomes denser than the egg, the egg will float.
Step-by-Step Guide
Follow these simple steps to make an egg float using salt:
- Begin by adding salt to your water. You'll need a glass or container and enough water to cover an egg. Start with 1 tablespoon and stir it until the salt dissolves.
- Continue adding salt. Gently place the egg in the water (or leave it in if it sank). Keep adding more salt until the egg floats. Stir well after each addition to dissolve the salt.
- Create Layers (Optional but cool!). For a visual demonstration of density layers, you can add plain water on top. Next, carefully pour more fresh water until the glass is nearly full (be careful to not disturb or mix the salty water with the plain water). Pouring over the back of a spoon held against the side of the glass can help keep the layers separate.
What Happens?
When you've added enough salt, the water at the bottom of the glass becomes very dense. The egg is now less dense than this salty water, so it floats on top of the dense layer. If you carefully add plain water on top, the less dense fresh water will sit on top of the denser saltwater layer, and the egg will float between the two layers, resting on the boundary where the density changes.
Key Tip for Success
The instruction to "be careful to not disturb or mix the salty water with the plain water" when adding the fresh water is crucial if you want to create distinct layers and have the egg float between them. Mixing will create a gradient or uniform density, and you won't see the layered effect clearly.
This experiment beautifully illustrates how changing the density of a liquid can affect whether an object floats or sinks.
