The gas received an amount of heat equal to 300 J and performed work equal to 400 J

The gas received an amount of heat equal to 300 J and performed work equal to 400 J. How did the internal energy of the gas change, if its mass is constant?

According to the first law of thermodynamics:

∆U = Q + A ‘, where Q is the amount of heat that was received – given the gas (Q> 0 and Q = 300 J, since heat is supplied to the system), ∆U is the change in the internal energy of the gas, A’ is the perfect work gas – over the gas (A ‘<0, A’ = -400 J, since the work was done by the system).

Let’s calculate the change in the internal energy of the gas:

∆U = Q + A ‘= 300 + (-400) = 300 – 400 = -100 J.

Answer: The internal energy of the gas decreased by 100 J.