I am little confused as to why temperature is a measure of thermal energy. Thermal energy is defined as the total internal kinetic energy of an object. Temperature, on the other hand, is defined as the measure of the average kinetic energy of an object, or the thermal energy per particle. If temperature only measures the average kinetic energy of each particle, then how does this measure thermal energy of an object, when there are other factors involved such as the size of the object. Say we have two containers of the same size. Container 1 has one particle moving at X m/s. Now imagine a second container. It as 10 particles moving at X m/s. Both of these containers have the same average internal kinetic energy, but container two has more internal kinetic energy. Could someone please explain why we use to temperature to measure thermal energy?