Density

Density refers to the thickness of a material. The thicker a substance is the higher the density. The thinner a substance is the lower the density. Air is a mixture of gases and is very thin. Therefore, it has a very low density. There is not much matter in any volume of air. Liquids are a little thicker than gases. So the density is higher than that for gases. You can move easily through a gas and not quite so easily in a liquid like water. Solids are very thick and so have a much higher density. You can=t move through a solid. Density is mass / volume. You will notice that you can select to solve for density, mass or volume. Check the appropriate option, enter the requested data and press Ok. 
