Solutions consist of two separate substances dispersed through each other. Relative amounts of the two substances can vary. Think weak coffee versus strong coffee. The amount solute compared to solvent or solution is concentration. The common phrase, "not from concentrate," is based on a qualitative understanding of concentration. Safe standards for various environmental toxins are normally expressed in part per million (ppm). This is a quantitative measure of concentration. This PowerPoint presentation defines concentration and describes qualitative and quantitative measures of concentration. Sample problems are provided to illustrate the calculation of concentration, percentage by mass, percentage by volume, and parts per million. (Molarity is covered separately.) Worksheets on this topic are available free of charge on my website at www.evanschemistrycorner.com.