The internal standard method is widely applied in quantitative analyses. However, most analytical chemistry textbooks either omit this topic or only provide examples of a single-point internal standardization. An experiment designed to teach students how to prepare an internal standard calibration curve is described. The experiment is a modified version of an experiment that uses the internal standard method to quantify the percentage of vinyl acetate in poly(ethylene-co-vinyl acetate). Students gain a good understanding of how to apply the internal standard method as the concentration of internal standard changes throughout the experiment. The experiment also provides students with hands-on experience with the use of Fourier transform infrared-attenuated total reflectance (FTIR-ATR) spectroscopy. (Contains 4 figures.)