The oceans have always been salty, although most lakes and ponds are not salty. Do things float the same way in a lake or on the ocean?
What You Need:
1. two fresh raw eggs
2. two drinking glasses
3. tap water
4. table salt
5. a small scale, like a postal rate scale
What You Do:
1. Fill one glass with tap water.
2. Fill the other glass with the exact same amount of tap water and add five heaping tablespoons of salt. Mix well.
3. Carefully crack open an egg and gently set it on the surface of the tap water. What happens to the egg?
4. Now set the other egg on the salty water. Does the egg do the same thing?
5. Weigh the two glasses, and compare them. Which weighs more? If you suspect that your eggs don’t weigh the same, try it again and weigh the water-filled glasses ahead of time.
The egg sinks in freshwater, but floats in salt water.
If you have the same amount of each, salt water weighs more than fresh water. There is more “stuff” in salt water than in the same amount of fresh water. We say salt water is denser than fresh water. The denser salt water can hold up the weight of an egg. But the fresh water doesn’t have enough “stuff” in it to support the same weight. Things float better in salt water than in fresh water because salt makes water heavier.