Activity:

Density Demonstration

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What You Need:

  • 2 eggs
  • 2 clear glasses
  • Measuring spoon
  • Table salt
  • Water

What You Do:

  1. Fill two glasses with water. 
  2. In one of the glasses put in a teaspoon of salt.
  3. Put an egg in each of the glasses and see what happens.
  4. Have your child record the behavior of the eggs in the two glasses.
  5. Experiment with adding more salt to the salted glass.

What's Going On Here?

 

Density measures matter relative to the volume of a substance, which in this case is water. The water that we drink usually has low density, but when you add salt it absorbs the water. To better understand why the egg in the salted glass floats it's useful to know that salt is a desiccant, which means that it absorbs water. So, when you put salt it water, the salt molecules fill up with water molecules. This interaction creates a layer of salt water and the egg, unable to penetrate the salt layer, floats.

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