Your students might be fans of peppers but not the hot ones. Nonetheless, the way of measuring the pungency or the spicy heat of chile pepper is an exciting study topic.
The Scoville scale is a method for measuring the heat level of chile peppers, and it was developed by an American chemist, Wilbur Scoville in 1912. The substance that makes peppers hot is called capsaicin, and is measured in Scoville Heat Units (SHU). Pure capsaicin is 15,000,000 SHU, while the capsaicin level of sweet bells is 0 SHU.
Finding out more about how Scoville created his scale, which is still used to measure the pungency of chiles and hot sauces, is a nice chemistry project idea. This chart could also be used in the biology classes when learning about one of our biological senses, taste.