# What floats and what sinks in water

Why do some bodies sink and others float in water? Let's look at some examples.

Water and oil do not mix. When a ship leaks oil, it causes major damage to nature. This is because oil does not sink. It floats on water, not allowing the passage of light essential for marine life.

If we put water in a container and inside it a piece of iron (nail), this iron will sink. Already if we put only an "empty" and capped bottle, the bottle will float. These examples show what density is.

In the first example, water is denser than oil. So what has the highest density is in the background. In the second example, the nail is denser than water, so it sinks. In the example of the empty bottle, it is actually full of air, which is less dense than water.

It is a relationship between the mass and volume of a substance. What weighs more? 1kg of cotton or 1kg of iron? The question leads one to think that the answer is 1 kg of iron because it is heavier, but in fact it is the densest.

Cotton and iron have the same mass (1kg), what will be different is the volume. A larger volume of cotton that corresponds to 1 kg and a very small piece of iron that corresponds to 1 kg. So:

denser - have greater mass at a given volume
less dense - have less mass at a given volume

d = m: v

### Density table of some substances:

 Substance Density in g / cm³ Water 1 Ice 0,91 Alcohol 0,8 Petroleum 0,85 Acetone 0,80 Glass 2,6 wood 0,5 Mercury 13,6 Aluminum 2,7 Silver 10,5 Lead 11,4 Gold 19,3 Iron 7,8 Air 0,0013 Zinc 7,1 Sea water 1,03

Density is also related to the proximity of substance molecules. If we compare water molecules we will see that they are more united (more concentrated) than oil molecules, less united (less concentrated). So it can be said that water is denser than oil because its molecules are more united and so there are more water molecules compared in the same volume.