A system increases in internal energy by 80 J and 50 J of work are done on it at the same time. What is the heat change of the system

The heat change of the system is 30 J.

Explanation:

Given;

increase in internal energy of a system, ΔU = 80 J

work done on the system, W = 50 J

The heat change of the system can be calculated from first law of Thermodynamics;

ΔU = Q - W

where;

Q is the heat absorbed by the system

W is the work done by the system (negative when work is done by the system and positive when work is done on the system)

Since work was done on the system the increase internal energy is given as;

ΔU = Q  + W

ΔU  - W = Q

80 J - 50 J = Q

30 J = Q

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