Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy is a useful technique for measuring the infrared spectra of solids and liquids as well as probing adsorption on particle surfaces. Several examples of the use of FTIR-ATR spectroscopy in different undergraduate chemistry laboratory courses are presented here. These examples include measuring the infrared spectra of solid and liquid organic compounds commonly used as unknowns and of inorganic solids synthesized by students. The use of ATR-FTIR spectroscopy in the upper-level physical chemistry laboratories will be discussed in Part II where a new experiment involving the adsorption of ions from solution onto oxide particle surfaces is introduced. In addition to the implementation of ATR-FTIR spectroscopy into the undergraduate curriculum, students involved in undergraduate research can use this technique to get high-quality publishable data on a number of interdisciplinary chemically-relevant interesting research projects. [For Part II, see EJ824966.] (Contains 3 figures.)