Density of water.How to demonstrate that the density of water can be changed using salt.
For instance, a classic test is to put a fresh egg into a glass of water. The egg will sink into the glass. If you'll add some salt in the water and you'll stir it to disolve the salt crystals, to create a salty solution, you'll notice that the egg will float in the salty solution.
Conclusion: If you want to increase the density of water, you'll have to dislove salt into water. The more salt you'll add, the more dense will be the solution resulted.