posted by kellie .
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,, :)