a system undergoes a process consisting of the following two steps:

step 1: the system absorbs 72 J of heat while 35 J of work is done on it.

step 2: the system absorbs 35 J of heat while performing 72 J of work

calculate delta E for the overall process.

214

144

To calculate the overall change in energy (ΔE) for the process, we need to consider both steps and their respective energy transfers.

In step 1, the system absorbs 72 J of heat (q1) while 35 J of work (w1) is done on it. The heat transfer in step 1 can be written as q1 = +72 J, indicating absorption of heat by the system. The work done on the system can be written as w1 = +35 J, indicating work being done on the system.

In step 2, the system absorbs 35 J of heat (q2) while performing 72 J of work (w2). The heat transfer in step 2 can be written as q2 = +35 J, indicating absorption of heat by the system. The work done by the system can be written as w2 = -72 J, indicating work being done by the system.

The overall change in energy (ΔE) can be calculated using the first law of thermodynamics:

ΔE = q1 + q2 + w1 + w2

Substituting the given values:

ΔE = (+72 J) + (+35 J) + (+35 J) + (-72 J)
= 144 J - 72 J
= 72 J

Therefore, the overall change in energy (ΔE) for the process is 72 J.

To calculate the change in internal energy (ΔE) for the overall process, we need to determine the net heat and net work done on the system.

In step 1, the system absorbs 72 J of heat while 35 J of work is done on it. This means that the system gains 72 J of energy from the surroundings through heat transfer, and 35 J of energy is transferred to the system through work. Therefore, the net heat transferred to the system in step 1 is 72 J - 35 J = 37 J (heat gained).

In step 2, the system absorbs 35 J of heat while performing 72 J of work. This means that the system gains 35 J of energy from the surroundings through heat transfer, and 72 J of energy is transferred from the system through work. Therefore, the net heat transferred to the system in step 2 is 35 J (heat gained), and the net work done by the system is -72 J (work done).

To find the overall change in internal energy, we add the net heat and net work together:

ΔE = Q + W

ΔE = (37 J + 35 J) + (-72 J)
ΔE = 72 J - 72 J
ΔE = 0 J

Therefore, the overall change in internal energy (ΔE) for the process is 0 J.