The properties of an aqueous solution are highly dependent upon the concentration of the solution. There are various ways to represent the concentration of a solution. For example, the concentration of alcohol in a beer is typically represented by % alcohol by volume, where liquor is commonly represented by proof. When chemists communicate concentration with each other they do so using units of Molarity, which is moles of solute per liter of solution.
4.5 Concentrations of Solutions
4.5 Concentrations of Solutions Example Problem
A common practice performed in larger labs is to purchase or prepare solutions at high concentrations then dilute them. When these dilutions occur the volume of the solutions change, but the number of moles remains constant.