According to the First Law of Thermodynamics, what is the relationship between internal energy and heat?

The First Law of Thermodynamics states that the change in internal energy of a system is equal to the heat added to the system minus the work done by the system on its surroundings. This can be succinctly represented by the equation:

ΔU = Q - W

where ΔU is the change in internal energy, Q is the heat added to the system, and W is the work done by the system. Based on this understanding, option C accurately reflects this relationship by indicating that the internal energy increases with the amount of heat added to the system reduced by the work done by the system. It emphasizes that an increase in internal energy can occur when sufficient heat is supplied to overcome the energy used to perform work.

Understanding this relationship is vital in thermodynamics as it highlights the conservation of energy within a closed system, where energy can neither be created nor destroyed, only transformed or transferred.