Answer to Question #329503 in Physical Chemistry for May

Question

1) The first law of thermodynamics is a version of the law of conservation of energy. What does this mean in terms of the exchange of heat and work in a closed system?

Answer 1

During an interaction between a system and its surroundings, the amount of energy gained by the system is exactly equal to the amount of energy lost by the surroundings.

A closed system can exchange energy with its surroundings only through heat and work

transfer.

In other words, the change of the energy of the system is always equal to the transfer of energy across the system boundary as heat and work. OR: The energy of a system remains unchanged if the system is isolated from its environment as regards to work and heat regardless of the nature of changes within the system.