Testing the pH of various liquids is one of the most popular activities in 5th- through 8th-grade classrooms. The author presents an extensive pH-testing lesson based on a 5E (engagement, exploration, explanation, extension, and evaluation) teaching model. The activity provides students with the opportunity to learn about pH and how it relates to the human digestive system. Students learn to use computer-assisted pH sensor technology to determine the acidity of liquids, thus overcoming the limitations of pH strips, which can be a source of error in measurement. The lesson allows students to understand how scientific research is highly dependent on technology because technological advances provide instruments and techniques that enable increasingly precise observation of objects and phenomena, whereas previous methods may have limited how much scientists could learn about certain subjects. (Contains 2 figures.)