we know that matter can exist in the form of pure substances like a compound or element or there can be mixtures of these pure substances a homogeneous mixture can also be called a solution and we want to be able to describe certain aspects of solutions whether we are describing the composition of the atmosphere or the amount of salt in seawater we need to be able to describe concentration this is the relative amount of a component present within a solution first let's go over some definitions the component of the solution that is present in the greatest amount is called the solvent in the case of seawater that would be the water and the component or components that are dissolved in the solvent are called solute in the sea water that would be the salt and anything else that isn't water molecules if there isn't much solute the solution is said to be dilute and if there is a lot of solute the solution is said to be concentrated if water is the solvent in a solution we call it an aqueous solution we will measure concentration in terms of molarity symbolized by a capital m this refers to the moles of a particular solute that are present per liter of solution we should be able to calculate the molarity of any substance given the moles of that substance and the total volume of the solution for example let's say that a 355 milliliter soft drink contains 0.133 moles of sucrose or table sugar what is the molar concentration of sugar in the soft drink well molarity is defined as moles solute per liter of solution so let's plug the numbers in 0.133 moles goes on the top because that's how much solute we have and as for the volume of solution this must be in liters so let's convert our 355 milliliters into 0.355 liters and put that on the bottom doing the math we should get 0.375 molar as the concentration of sugar in the drink this kind of information is useful because we could then calculate the amount of sugar that would be in any volume of the soft drink or the volume of soft drink it would require to provide a particular amount of sugar and now we know how to calculate molarity