The more the particles vibrate or move, the hotter the material.

Therefore the particles have kinetic energy and potential energy due to their inter-molecular bonds. Inside any solid, liquid or gas at any temperature above absolute zero, the particles are constantly moving in a gas the particles move freely in random directions, in a solid they vibrate about a fixed position. Temperature difference can be thought of as the driving force behind heat flow. Two or more bodies are said to be in thermal equilibrium if they are at the same temperature and there is no net flow of energy between the them. The ice lolly will absorb heat from the room and will melt as it reaches thermal equilibrium.

So as heat flows from the cup of tea to the room and it loses heat its temperature drops and it will reach thermal equilibrium with the room when they are at the same temperature. Figure 2: The hot tea will radiate heat away to the cooler room, whereas the cold ice lolly absorbs heat from the room If we leave a hot object and a cold object out in a room which is at normal room temperature, there will be a flow of heat from the hot object into the room and a flow of heat from the room into the cold object. If there is no flow of energy there is very little sense of talking about heat. Heat is defined as the flow of energy from a warmer body to a cooler one. Figure 1: Heat always flows from hotter bodies to cooler boddies

If we put a hot object in thermal contact with a cold one, heat will flow from the hot object to the cold one. Two objects can have different amounts of heat, but have the same temperature, and vice-a-versa two object can have very different temperatures, but have the same amount of heat. Heat and temperature are easily confused, but it is important to understand the difference.

Stick with it as the theory behind this module is pretty simple and the maths is surprisingly satisfying. Although brief, the module contains quite a lot of maths, especially on this page, when discussing the transfer of heat, and also when deriving the equations of kinetic theory. This module, Thermal physics, focuses on the transfer of thermal energy and its effect on temperature and the state of the material.

Drops in the bucket homework