This lesson begins with a story about rescuing reptile eggs from a new construction site. Using the story as motivation, students are presented with an engineering design challenge: Build a portable device that can warm, support, and protect one reptile egg as it is moved from a construction site to a nearby reptile conservation center. After observing different heat packs, students discuss the criteria and constraints related to designing a heat pack as the basis for their device. Students investigate calcium chloride as an exothermic dissolver and then move on to calcium chloride and baking soda as the exothermic chemical reaction which will serve as the heat source for their device.
Students adjust the amounts of the reactants (water, calcium chloride, and baking soda) to achieve the right temperature range and then test a prototype in a sealed zip-closing plastic bag. Students use their findings and ideas about insulation and heat transfer to draw an optimized design that 1) Keeps an egg at the ideal temperature, 2) Holds an egg in the proper orientation, and 3) Protects the egg from impact. Each student or student group draws this device and explains how the device meets each of the three criteria.
