Salinity of Water and Density
In this activity, you will test the density of salt water compared to freshwater. Before you start the test, you will answer a few questions about salinity, a measure of the amount of dissolved salts in water.

Estimated time to complete: 1 hour
You will need these materials:

food coloring (1 color)
a 1-cup measuring cup
1 sheet of colored construction paper
a clear plastic or glass container, large enough to hold 4 cups of water
a drinking glass
8 teaspoons salt
a teaspoon
4 cups water at room temperature
Hypothesis and Data Collection
Measure 2 cups of water and pour it into the plastic container. Then measure 2 more cups of water pour into the drinking glass. Add 6 to 8 teaspoons of salt to the water in the glass. Stir until the salt is dissolved. Add 3 to 5 drops of food coloring to the salt water and stir until the water is a uniform color. Move on to part A.

Part A
What do you think will happen when you mix the salt water with the water in the plastic container?
Part B
Now pour the salt water into the plastic container with the tap water. Write down your observations.
Analyze and Extend
Part A
Did your observations match your predictions when you mixed the water?
Part B
What caused the change that you saw in the water mixture?
Part C
The equation for density is density = mass ÷ volume. Explain what happened in your experiment in terms of density, mass, and volume when you added the salt.
Part D
If you repeated the experiment with a glass of water that had 5 teaspoons of salt and another glass that had 10 teaspoons, what do you think would happen?
Part E
How does this experiment relate to the evaporation of salt water in the ocean?