Liquids of Different Densities
The following experiment is not showy like some that. It is very important, having far-reaching effects in our daily life. It is quite simple. You take a bottle and pour into it a quantity of oil-any kind will do, as long as it is slightly coloured. Then you add some water and, if you have any, it will be useful to add some mercury. Now cork the bottle and give it a thorough shaking; then let it stand for half an hour. At the end of this time you will find that, in spite of the shaking, the three liquids have sorted themselves out and stand in layers in the bottle. Why?
The reason is that the three liquids possess different densities. The mercury is the heaviest and the water is heavier than the oil. You need not waste the substances after the experiment is done. The oil can be poured off into a bottle, the water will not be wanted and may be thrown down the sink, and the mercury is easily returned to its original bottle.