Final answer:
The first law of thermodynamics states that the change in internal energy of a system is equal to the net heat transfer into the system minus the work done by the system, formulated as ΔU = Q - W.
Step-by-step explanation:
The first law of thermodynamics states that if Q is the heat flowing out of a system, W is the work done by the system on its surroundings, and ΔU is the decrease in internal energy of the system, then the first law of thermodynamics can be stated as ΔU = Q - W. This law represents the principle of conservation of energy, asserting that energy cannot be created or destroyed in an isolated system. The energy of a system is conserved through the exchange of heat and work, where heat absorbed by the system is considered positive, and work done by the system is also positive, indicating that energy is leaving the system.
The formula ΔU = Q - W suggests that the change in internal energy (ΔU) of a system is equal to the net heat transfer (Q) into the system minus the net work (W) done by the system. This relationship is crucial when calculating the changes in energy for processes in thermal equilibrium.