In our last lecture we discussed properties (length, volume) of systems (solids, liquids or gases) at different temperatures, and how those properties changed as the temperature of those systems changed. One thing that we did not address in that lecture was how we were to change the temperature of the systems.  How do we change the temperature of an object, anyway?

We discussed previously the microscopic view of temperature – it is a measure of the average kinetic energy (the energy of motion) of atoms or  molecules making up the system.  It should then be clear that, in order to increase the temperature of a system of objects, we must increase the energy of the atoms or molecules in that system. In order to do this, we must transfer energy from one system (the system providing the energy) to the other (the system whose temperature we want to increase).  (The reverse process takes place to lower the temperature, of course.)  There are three ways to transfer energy, called modes of energy transfer.  The  first section in this lecture introduces these modes of transfer, and then we start our discussion of what happens to systems as energy is transferred to them.  This will take us to the topics of specific heat,  phase changes, and latent heats. Putting all of this information together then leads us to the topic of calorimetry, which will end up this lecture.