According to the second law of thermodynamics, during any process the change in entropy of a system and its surroundings is either zero or positive. Thus the entropy of the system has increased. Although no energy has been lost by the heat transfer, the energy can no longer be used to do work. Furthermore, the combined lukewarm bodies cannot unmix themselves into hot and cold parts in order to repeat the process. This heat flow can be utilized by a heat engine (device which turns thermal energy into mechanical energy, or work), but once the two bodies have reached the same temperature, no more work can be done. If the bodies are placed in contact, heat will flow from the hot body to the cold one. For example, consider a system composed of a hot body and a cold body this system is ordered because the faster, more energetic molecules of the hot body are separated from the less energetic molecules of the cold body. Click the link for more information.В in terms of heat and temperature, entropy indicates the degree to which a given quantity of thermal energy is available for doing useful work-the greater the entropy, the less available the energy.

Historically, it grew out of efforts to construct more efficient heat engines-devices for extracting useful work from expanding hot gases. Originally defined in thermodynamics thermodynamics,Д«ranch of science concerned with the nature of heat and its conversion to mechanical, electric, and chemical energy. Click the link for more information.В or information. Energy and work are measured in the same units-foot-pounds, joules, ergs, or some other, depending on the system of Forms of energy include heat, light, sound, electricity, and chemical energy. In physics, the ability or capacity to do work or to produce change. Entropy (Д•n`trЙ™pД“), quantity specifying the amount of disorder or randomness in a system bearing energy energy,

Entropy change