Calculate the change in internal energy for a system that absorbs 242 J of heat and does 193 J of work on the surroundings...
internal energy, U, is the sum heat, Q, and work, W:
U = Q + W
U = 242 - 193
U = + 49 J
>>>sign conventions for U = Q + W:
*heat absorbed by the system is (+)
*heat released by the system is (-)
*work done BY the system is (-)
*work done ON the system is (+)
*work done BY the surroundings is (+)
*work done ON the surroundings is (-)
but note that in some books the formula for internal energy is U = Q - W
so there,, :)
To calculate the change in internal energy for a system, you can use the First Law of Thermodynamics, which states that the change in internal energy (ΔU) is equal to the heat added to the system (Q) minus the work done by the system (W).
Mathematically, the formula for the change in internal energy is:
ΔU = Q - W
In your case, the system absorbs 242 J of heat (Q = 242 J) and does 193 J of work on the surroundings (W = 193 J). Let's substitute these values into the formula:
ΔU = 242 J - 193 J
Now, we can simply subtract the work from the heat absorbed to find the change in internal energy:
ΔU = 49 J
Therefore, the change in internal energy for the system is 49 J.