What is the change in internal energy if 30 j of thermal energy is released
from a system, and the system does 40 j of work on the surroundings? use a
u= q-w.

ΔU = -70 J

Explanation:

ΔU = Q − W

where ΔU is the change in internal energy,

Q is the heat absorbed by the system,

and W is the work done by the system (on the surroundings).

30 J of thermal energy is released, so Q = -30 J.

40 J of work is done by the system, so W = 40 J.

Therefore, the change in internal energy is:

ΔU = -30 J − 40 J

ΔU = -70 J

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