This is an excellent lesson to use when introducing high school students to percent concentrations. Health Science students especially need to understand concentrations and dilutions calculations because these calculations are regularly made by health care personnel. The lesson features resources that will benefit visual learners. Resources include an overhead graphic illustrating the mixing of two substances with different concentrations and an interactive mixture applet designed to help students understand the “how” of percent calculations which is preferable to just providing a formula and instructions for “doing” the calculation. (jrs)