Tiny Dead Sea10 minutes
There is a big difference between tap water and seawater. Seawater contains salt, which has an effect on how easy it is to make something float in it – whether it’s an egg, or something as large as a ship.
Pour water into a glass. Put the egg in it. Does the egg float?
Use the spoon to slowly add salt to the water, a little bit at a time, until the egg starts to float. Carefully stir the salt through the water. Make sure you don’t break the egg!
What did you discover
Liquids exert an upward force on any object you place in them. How strong this force is depends on the liquid. If the upward force is not very great, the object sinks. By adding salt to water, the upward force will increase, until it becomes strong enough for the object to float up.
The same goes for ships. The hull of a ship floating in seawater, which contains salt, will stick up above the waterline more than it would in fresh water, which doesn’t contain salt. The Dead Sea, in the Middle East, contains almost ten times as much salt as the ocean. If you go swimming there, you can float on the surface without any effort – just like a boat.