Concentration, solute mass and volume are tied together

1. The three quantities are linked by $c=\frac{m}{V}$, so knowing any two lets you find the third.
2. Concentration $c$ is in $g/{dm}^3$, mass $m$ is in grams and volume $V$ is in ${dm}^3$.

More solute raises the concentration

1. At a fixed volume, concentration is directly proportional to the mass of solute.
2. Doubling the mass of solute in the same volume doubles the concentration.

A larger volume lowers the concentration

1. At a fixed mass of solute, concentration is inversely proportional to the volume of solution.
2. Adding more solvent dilutes the solution, so the same solute spread through a bigger volume gives a lower concentration.

Rearranging to find a mass or a volume

1. To find a mass of solute, use $m=c\times V$.
   1. In $200{cm}^3$ ($0.2{dm}^3$) of a $15g/{dm}^3$ solution, the mass of solute is $15\times 0.2=3g$.
2. To find a volume, use $V=\frac{m}{c}$.
   1. A $25g/{dm}^3$ solution holds $10g$ of solute in $\frac{10}{25}=0.4{dm}^3$, which is $400{cm}^3$.