What type of energy change is represented in the first law of thermodynamics?

The first law of thermodynamics, also known as the law of energy conservation, states that energy cannot be created or destroyed, only transformed from one form to another. This is best represented by the mutual conversion of work and internal energy, which means that the energy added to a system in the form of heat can change the internal energy of the system, and this internal energy can also be converted into work.

This principle illustrates that any increase or decrease in the internal energy of a system can be attributed to the net heat added to the system and the work done by or on the system. The emphasis here is on the interrelationship between work and internal energy, confirming that energy is conserved within a closed system.

The other options focus on more specific forms of energy conversion. While converting heat energy into mechanical energy is a fundamental application of the first law, it is a narrower view of the broader relationship established in the first law. Similarly, the transformation of kinetic energy into potential energy represents specific scenarios that do not encompass the entire scope of the first law. Changes in chemical energy refer specifically to reactions that involve energy changes but do not illustrate the comprehensive relationship defined by the first law concerning internal energy and work.