Heat Transfer Changes in Temperature ThermoChemistry Heat Transfer Changes in Temperature

Introduction A system can only change temperature if there is a flow of heat energy either in or out of the system. If heat energy flows into the system, we expect the temperature to rise. If heat energy flows out of the system, we expect the temperature to fall.

We have terms to describe these events. q “endothermic” q “exothermic” There will be more on this endothermic and exothermic stuff later in the unit.

The math associated with this: Obviously, there is a connection between the magnitude of the heat flow and the magnitude of the associated temperature change.

Here is the Equation The relationship between the heat flow and the change in temperature of the system is given by the equation: qflow = m • C • ΔT Where: qflow is the heat flow in Joules… C is the same specific heat that we defined in the first section of the unit (it will have units of J/g•⁰C) … and ΔT is the resulting change in temperature in degrees Celsius.

Important Notes: m C ΔT qflow The change in temperature is not an actual temperature – it is an indication of how much the temperature of the system will change. When reading these problems, be sure to look for the “change words” – they will tell you that you have a dynamic system and that you will need a ΔT as part of the problem. qflow m C ΔT