# How does density differ from concentration?

${\rho}_{\text{density"="Mass per unit volume}}$...and thus units of $g \cdot m {L}^{-} 1$ or $g \cdot c {m}^{-} 3$...
Whereas $\text{concentration}$ is the amount of substance contained in solution a VOLUME of LIQUID or GAS. Typically, we gots units of $\text{parts per million}$, $m o l \cdot {L}^{-} 1$, $\text{percentage by mass}$...