Heat and Work

The distinction must also be made among the energy terms heat and work. Both symbolize energy in transition. Work is the transfer of energy resultant from force acting via a distance. The heat is energy transferred as the outcome of a temperature difference. Neither heat nor works are thermodynamic property of a system. The heat can be transferred into or out of a system and work can be completed on or by a system, though a system cannot have or store either heat or work. The heat into a system and work out of a system are believed positive quantities.

Whenever a temperature difference exists across the border, the Second Law of Thermodynamics points out the natural flow of energy are from the hotter body to the colder body. The Second Law of Thermodynamics rejects the possibility of ever entirely converting into work all the heat supplied to a system operating in a cycle. The Second Law of Thermodynamics, explained by Max Planck in 1903, defines that:

It is not possible to build an engine which will work in a complete cycle and generate no other effect apart from the increasing of a weight and the cooling of a reservoir.

The second law states that when you draw heat from a reservoir to increase weight, lowering the weight will not produce sufficient heat to return the reservoir to its original temperature, and ultimately the cycle will stop. When two blocks of metal at various temperatures are thermally insulated from their surroundings and are fetched into contact with each other the heat will flow from hotter to colder. Ultimately the two blocks will reach similar temperature, and heat transfer will finish. Energy has not been lost, though rather some energy has been transferred from one block to the other.