Adiabatic process? What is the change in the system’s internal energy?

Question

An ideal gas system undergoes an adiabatic process in which it expands and does 20 J of work on its environment. What is the change in the system’s internal energy?

a. –20 J

b. –5 J

c. 0 J

d. 20 J

Answer 1

Heat transfer to the system = work done by the system + change in internal energy of the system

For adiabatic process, heat transfer to the system = 0

Therefore

change in internal energy = - work done = -20 J

Ans (a)