The “Cool Off” challenge is a formative assessment tool for learning about how students think about chemical causality. It has been tested with middle school and high school students, and with preK-12 science teachers. It provides participants the opportunity to think creatively about a science challenge, and then test their predictions in the lab.
This formative assessment requires a laboratory setting (with proper safety precautions) and about 1 hour of time. For each team of students, you will need two metal temperature probes with digital readouts. Handheld popsicle thermometers work, as do individual digital thermometers connected to LED displays. The student in the photo is using an interface with two ports, each with a temperature probe attached, and there are two temperatures on the display. Try to provide a variety of liquid substances. We typically provide water, acetone or nail polish remover, canola or other oil, ethanol or rubbing alcohol, hand sanitizer, vinegar, carbonated beverages… We have found it to be particularly productive for participants when all of the liquids look similar (i.e., transparent like water), because it seems to get participants to think more about how the identity of the substance has something to do with how the cooling works. However, teachers should feel free to include any materials that they believe will stimulate interesting chemical thinking by their students.
The challenge for students is presented in the one-page handout below. Be sure to pay attention to the safety precautions. Students should wear goggles and gloves.
