Question

A cylinder and piston assembly (defined as the system) is warmed by an external flame. The contents of the cylinder expand, doing work on the surroundings by pushing the piston outward against the external pressure. If the system absorbs 551 J of heat and does 478 J of work during the expansion, what is the value of ΔE?

Answer 1

Answer:

ΔE = 73 J

Explanation:

By the first law of thermodynamics, the energy in the system must conserved:

ΔE = Q - W

Where ΔE is the internal energy, Q is the heat flow (positive if it's absorbed by the system, and negative if the system loses heat), and W is the work (positive if the system is expanding, and negative if the system is compressing).

So, Q = + 551 J, and W = + 478 J

ΔE = 551 - 478

ΔE = 73 J