In short
Density is the mass of a material in each unit of its volume, . It is measured in kilograms per cubic metre ().
A dense material packs a lot of mass into a small volume. Lead is denser than wood, so a small piece of lead is heavier than a small piece of wood. An object floats in a fluid if its average density is less than the fluid's. Density changes with temperature, because most materials expand when they are heated. Relative density is the ratio of a material's density to the density of water.
A block has a mass of and a volume of . Its density is , the density of aluminium.
Also searched as: planet density, planets ranked by density.
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