The floating egg – what’s behind it?

Two glasses each filled with water and an egg, one egg floats

This could almost be a magic trick: Normally, eggs sink in water. But with a little trick you can make an egg float. We'll show you how it works.

Before you get started

If you are experimenting at home:
1. Let your parents know and discuss the experiments with them beforehand.
2. Do not eat or drink at your workspace.
3. Wash your hands thoroughly before and after the experiment.
4. Be careful and cautious with the materials.

Graphic figure boy pouring liquid in flask

Bottle with water, two eggs, two glasses and a jar with salt and a spoon

You will need

2 Eggs
2 Glasses
Spoon
Salt
Water

Let’s get started

Two water-filled glasses, each with an egg; the eggs lie at the bottom of the glasses.

1. Immerse eggs in glasses with water

Take two eggs and two glasses and place one egg in each glass. Carefully fill the glasses with warm water until the eggs are completely covered with water.

Two glasses, each filled with water and an egg. On the right side is a part of a hand holding a teaspoon with salt, which is placed in the right glass.

2. Add salt

Now add about four to five heaped teaspoons of table salt to one of the two glasses.

Two glasses, each filled with water and an egg. On the right side is a part of a hand stirring the salt added to the right glass with a teaspoon.

3. Dissolve the salt

Stir carefully. Wait until the salt has almost dissolved and observe what happens.

4. The egg floats!

When the salt is almost completely dissolved, the egg begins to float to the surface. You've done it!

Did you know?
Why does the egg start to float in salt water?

Answer

It has to do with something called "the density" of materials or objects. The less space ‏(volume) a given amount of weight ‏(mass) of a material takes up, the greater its density. A 100 g bar of chocolate is quite small. In contrast, 100 g of cotton candy is quite a big pile. So, chocolate has a greater density than cotton candy. Because a chicken egg has a greater density than water, it sinks in water. When we add salt to water, we change the density of the water at the same time. The more salt we add, the greater the density of the salt water. When the salty water reaches a density greater than that of the egg’s, the egg begins to float.

Maybe you have experienced the effect yourself. When you bathe in the salty sea, it is relatively easy to float on the surface of the water. This is most extreme at the Dead Sea: there, people even lie down in the water while reading a newspaper, without having to make swimming movements to keep themselves afloat.