A system with an increase in internal energy of 80 J and at the same time has 50 J of work done on it by the surrounding. What is the heat change of the system?

1 answer

The first law of thermodynamics states that the change in internal energy of a system equals the heat added to the system minus the work done by the system:

ΔU = Q - W

where:

ΔU = change in internal energy
Q = heat added to the system
W = work done by the system

In this case, we have:

ΔU = 80 J
W = -50 J (since work is being done on the system by the surroundings, the sign is negative)

So, we can rearrange the equation to solve for Q:

Q = ΔU + W

Q = 80 J + (-50 J)

Q = 30 J

Therefore, the heat change of the system is 30 J.