Make Water Denser
Objective: The student will see how it is possible to increase the density of water and thereby improve its floating powers.
Procedure: Place a fresh egg in a jug of clean water and the egg will sink to the bottom. Stir salt into the jug of water, about an eggcupful of salt to half a pint of water. Replace the egg and this time it will float because you have increased the density of the water. If you have a block of ice, float this in the salt water and you will notice that more of the ice shows above the brine than when it floated in fresh water.
Observation: Write your observations in your journal for both fresh and salty waters.
Challenge: If you are a swimmer, you have noticed how much easier it is to semi in the sea; provided it is calm than in fresh water. Why should this be?