Intro of Density

Different densities of fluids.

Density is something that affects many of our everyday decisions. Consciously or not, we make mental calculations of density every time we interact with the physical world around us. Can we slide that box? Can we lift that rock? 

People are often confused about the difference between weight and density. There is an old riddle which highlights this confusion: “What weighs more – a pound of feathers or a pound of lead?” The answer, of course, is that both weight same – one pound. However, feathers are much less dense than lead, and therefore take up much more space. Density is the ratio of an object’s mass to its volume. This means that to find density, you must measure an object’s mass and divide it by the amount of space it takes up. The standard units of density are [kg/m3], although other units are commonly used such as [g/ml], [g/cm3], or [kg/l]. 1 ml has the same volume as 1 cm3.