b) Calculate the change in the internal energy for a process in which a system absorbs 140 J of heat from the surroundings and does 85 J of work on the surroundings.

[tex]\[ \Delta U = q - w \][/tex]

[tex]\[ \Delta U = 140 \, \text{J} - 85 \, \text{J} \][/tex]

[tex]\[ \Delta U = 55 \, \text{J} \][/tex]



Answer :

To solve the given problem step-by-step, we need to calculate the change in thermal energy for a process where the system absorbs heat and performs work on the surroundings. We'll use the following formula:

[tex]\[ \Delta E_{thermal} = q + w \][/tex]

where:
- [tex]\( q \)[/tex] is the heat absorbed by the system
- [tex]\( w \)[/tex] is the work done by the system

According to the problem, the system absorbs 140 J of heat from the surroundings and does 85 J of work on the surroundings. Let's identify each component:
- [tex]\( q = 140 \)[/tex] J (heat absorbed)
- [tex]\( w = 85 \)[/tex] J (work done)

Now, plug these values into the formula to find the change in thermal energy:

[tex]\[ \Delta E_{thermal} = q + w \][/tex]

Substitute the known values into the equation:

[tex]\[ \Delta E_{thermal} = 140 \text{ J} + 85 \text{ J} \][/tex]

Perform the addition:

[tex]\[ \Delta E_{thermal} = 225 \text{ J} \][/tex]

Therefore, the change in the thermal energy for the process is:

[tex]\[ \Delta E_{thermal} = 225 \text{ J} \][/tex]