The same mass takes up a bigger volume - this means the gas is less dense. Density also depends on the material. A piece of iron with the same dimensions as a piece of aluminium will be heavier ...

Density describes how closely packed the particles are in a solid, liquid or gas. There is little difference between the density of a liquid and its corresponding solid (eg water and ice). This is ...

Bone density is a measure of the amount of minerals, such as calcium, in the bones. Bones with higher levels of minerals are stronger and less likely to break than bones with fewer minerals.