A lactometer is an instrument used to test the purity of . (Water/milk/mercury)

The relative density of a substance is the ratio of its density to the density of water at _____$°\mathrm{C}$.

When a substance is heated, its _____ increases. (Volume/mass)

The density of gases is more than that of solids.

The volume of any liquid completely filled in a relative density bottle remains the same.

The density of a substance is the ratio of its density to the density of water at $4{ }^{\mathrm{o}}\mathrm{C}$.

On multiplying the relative density by $1000$, one gets the density of a substance in $\mathrm{kg} {\mathrm{m}}^{-3}$.