August 28, 2013
This activity can help refresh your students on the scientific method and provide some biological context to the "chemistry of life" content that often kicks off the school year. Perspiration is critical to human evolutionary history and the endurance it enables is arguably on par with cognitive abilities as Homo sapien superpower.
This quick activity reminds students about the biological importance of waters properties and gets them thinking on the molecular level. Students immerse a Temperature Sensor into three different liquids; water, rubbing alcohol, and vegetable oil. They then graph the cooling curve once the probe is removed. The intermolecular forces play a big role in the energy it takes for the compounds to change state. Ask your students to do some research and explain how these forces connect with their data, or do some macro-scale modeling with a quick game of red-rover! The student version of the lab is available below.
Sample data from the lab using water, vegetable oil, and rubbing alcohol.
Analysis of the rubbing alcohol, with only the cooling portion of the curve selected.
Sample data table with user entered data.
Students could easily expand the investigation to other materials to create an inquiry. Depending on the student level you can also enhance the analysis questions and challenge students to explain the evolutionary significance of this adaptation, or dig further into the chemical properties of each compound.
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You’re probably familiar with the effects of perspiration on the skin. It cools you off during a run, or on a hot summer day. But why does perspiration make you feel cool? Let’s investigate.