Is it easier for an object to float in salt water or fresh water?

What You Need:

  • Fresh, uncooked egg
  • Large drinking glass
  • Water
  • Table salt
  • 2 teaspoons

What to Do:

1. Fill the drinking glass half full of water.

2. Carefully put the uncooked egg in the water. It should sink.

3. Add salt into the water one teaspoon at a time and stir carefully until it dissolves. *Do not take the egg out while you are adding the salt.

Question: How many teaspoons of salt do you have to add before the egg floats?

4. Now that the egg is floating, take a clean teaspoon and add one teaspoon of water at a time until the glass is almost full. The egg should float between the two layers of water; the salt water on the bottom and the fresh water on the top.

5. Try repeating the experiment using different items such as a piece of potato, a penny or a marble.

Abridged from:
Science is…A source book of fascinating facts, projects and activities. Second edition. Susan V. Bosak with Douglas A. Bosak and Brian A. Puppa. Scholastic Canada Ltd. 1992. P. 56.