Physical Chemistry Lesson of the Day – The First Law of Thermodynamics
January 6, 2014 Leave a comment
The change in internal energy of a system is defined to be the internal energy of a system in its final state subtracted by the internal energy of the system in its initial state.
However, since we cannot measure the internal energy of a system directly at any point in time, how can we calculate the change in internal energy?
The First Law of Thermodynamics states that any change in the internal energy of a system is equal to the heat absorbed the system plus any work done on the system. Mathematically,
Recall that I am using the sign convention in chemistry.
The value of and can be positive or negative.
- A negative denotes heat released by the system.
- A negative denotes work done by the system.