Question

Calculate the change in internal energy of the following system: A balloon is cooled by removing 0.659 kJ of heat. It shrinks on cooling, and the atmosphere does 385 J of work on the balloon.

Answer 1

-310J

Step-by-step explanation:

The change in internal energy (ΔE) of a system is the sum of the heat (Q) and work (W) done on or by the system. i.e

ΔE = Q + W ----------------------(i)

If heat is released by the system, Q is negative. Else it is positive.

If work is done on the system, W is positive. Else it is negative.

In this case, the system is the balloon and;

Q = -0.659kJ = -695J [Q is negative because heat is removed from the system(balloon)]

W = +385J [W is positive because work is done on the system (balloon)]

Substitute these values into equation (i) as follows;

ΔE = -695 + 385

ΔE = -310J

Therefore, the change in internal energy is -310J

PS: The negative value indicates that the system(balloon) has lost energy to its surrounding, thereby making the process exothermic.