Question

A thermodynamic system undergoes a process in which its internal energy decreases by 500 joules. At the same time, 220 joules of work is done on the system. What is the amount of heat transferred to or from the system?
280 joules
720 joules
-280 joules
-720 joules
0 joules

Answer 1

It requires energy to do work, and doing work on a system involves adding energy to that system. Does that help?

Answer 2

like PsiSquared said:
work done on a system adds energy to it, work done by the system means system loses energy so:
\[E_{final}=E_{initial}-500+220=E_{initial}-280 => \Delta E = -280 J\]
in other words the system has lost 280 Joules of Heat (Energy).

Answer 3

Answer is -280 joules

Answer 4

Answer is -280 joules