This is a quick and easy experiment to test the theory that salt water is more dense than fresh water.
All you need is:
For a simple control, we filled on cup with fresh water and then watched while we added the food coloring. The colors mixed pretty quickly.
Then we took another cup of water and added salt....Luke wanted to add a lot of salt, so we discussed the difference between a saturated and super saturated solution.
He mixed and mixed the salt and water....after a while we decided it was so super saturated we needed to dump off the saturated water into another clear cup, leaving a lot of salt in the bottom of the original cup.
We then added fresh water ice cubes to the salt solution. They floated at the top of the salt water and began to slowly melt.
Next, drop about 5 drops of food coloring into the cup....the food coloring remained entirely at the top of the cup in the fresh water and ice cubes.
At this point I felt we needed another "control"...so we got a glass of fresh water, added ice cubes and then food coloring.
The kids were amazed at how fast the food coloring squeezed between the ice cubes and colored all the fresh water blue.
Conclusion, salt water is much more dense than fresh water, in fact, the salt water never allowed the food coloring to reach below the ice cubes, and as the ice melted the blue color remained at the top of the cup in fresh water.
Another successful science experiment!