Concentration

These glasses containing red dye show changes in concentration. The solutions on the left are more diluted, and the solutions on the right are more concentrated.

In chemistry, concentration is how much of a substance is mixed with another substance.

The substance that is dissolved (i.e., the red dye in the example) is known as the solute. The substance in which the solute is dissolved (i.e., the water in the example) is known as the solvent.

To concentrate a solution, one must add more solute, or reduce the amount of solvent. To dilute a solution, one must add more solvent, or reduce the amount of solute.