Question

If a system has 475 kcal of work done to it, and releases 5.00 × 102 kJ of heat into its surroundings, what is the change in internal energy of the system?

Answer 1

Internal energy change = \[U = Q+W\]
Q = heat,
W = work

A few things you should know:

now if the work is done by the system it's negative.
if work is done to the system it's positive

if heat comes into the system it's positive.
if heat flows out of the system it's negative.


work is done to the system 475kCal so it's positive
we convert those to joules
2.0x10^3 kilo-Joules.

heat is released, so it's negative.
-5.0x10^-2KJ

combine these together

\[-5.0x10^{2}kJ + 2.0x10^{3}kJ = 1.5x10^{3}kJ\]

Answer 2

Combine what together?

Answer 3

We add the work and the heat together