Rumor has it that you can float more easily in the ocean than in a lake. Have you ever had the chance to try this in real life? Maybe on vacation?
Let’s try the following experiment to find out the truth ... and why!
Materials
Two jars of the same size (approximately 1 pint or 16 ounces)
Warm water
3 tablespoons salt
A spoon
Two eggs
Instructions
Fill both jars about halfway with warm water (about 1 cup).
Set one jar aside as your freshwater lake.
Make your ocean by adding 3 tablespoons of salt to the other jar. Stir until the salt dissolves.
Gently add one egg to each jar.
Notice where the eggs end up.
How it works
The egg in the “freshwater lake” should sink right to the bottom. But the egg in the “saltwater ocean” should float. You’re observing density in action. Density measures the volume of something in relation to its mass. Or, how heavy something is compared to its size. Two items can be the same size, like a golf ball and a ping pong ball, but very different weights. The heavier one, in this case the golf ball, is denser.
An object will float if it is less dense than the liquid it is in. The ability to float can also be called buoyancy. Because the egg sinks in the “freshwater lake,” it is more dense. But by adding salt, the density increases. The saltwater becomes more dense than the egg, so it floats, or becomes buoyant.
Can you make the egg sink by adding more freshwater? How much salt do you have to add to the fresh water to make the egg start to float? Can you make them both float in the middle?
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