In this experiment students explore how the cooling rates of objects depend on the surface area and volume of an object.
Students then compare the cooling rates they measure for objects of different sizes.
Before performing the experiment, it is important to discuss with the class the variables that determine the rates that objects cool. You might begin by having the students list and discuss the factors that determine the rate at which an object cools. In the case of the clay spheres, these factors would include, clay density, size, shape, surface area, and volume, as well as thermal conductivity of clay, initial temperatures of clay and of surrounding medium, in this case water. The instructor should emphasize the process of doing an experiment, namely, that all variables except one are controlled for each experiment performed. For each experiment all variables except temperature are controlled.