The system can be a single piece of matter or a collection of matter.
HEAT is the most common form of energy and is associated with the motion of particles of matter.
The faster the motion of the particles of an object the greater its heat content. A lit match and a forest fire may both be at the same temperature, but there is a considerable difference in the amount of heat each contains. The temperature of a system determines its ability to transfer heat to or acquire heat from another system. We may touch an object and describe its temperature as either neutral, warm, hot, cool or cold. However, if we need to know the precise temperature, we need to use a device known as a thermometer.