What do you think? Is saltwater denser than fresh water?

All you need is:

• 1/4 cup salt
• 2 cups water
• 2 clear 16 oz. glasses
• eye dropper
• food coloring
• 2 eggs
  

Here's what you do:

1. Fill glass with 1 cup of water.
2. Drop egg in glass. What happens?
3. Fill a second glass with 1 cup of water. Add salt and stir until dissolved.
4. Add a few drops of food coloring. Let sit for 5 minutes.
5. Add more water carefully by trickling it along the side of the glass so as not to disturb the settled colored saltwater. You may wish to use the eye dropper to add the water gently.
6. Drop egg in glass. What happens?
7. Compare how the eggs float in the two glasses. What's the difference? Why?

Here's how it works:

The reason the egg acts differently in saltwater is because of density (the weight of the liquid divided by the amount of space it occupies). The egg has a greater density than freshwater, so it sinks. When salt is added to the water, its density becomes greater than that of the egg. This means that the egg will begin to float.

Information provided by: http://www.onr.navy.mil