What is the relationship between heat and work according to the first law of thermodynamics?

The first law of thermodynamics, which states that energy cannot be created or destroyed but only transformed from one form to another, highlights the relationship between heat and work as forms of energy transfer. According to this law, both heat and work are recognized as methods of energy transfer into or out of a system.

Option C correctly encapsulates this concept by asserting that heat and work are both forms of energy transfer and can be converted into one another. For example, in a heat engine, heat energy (from burning fuel) is converted into work (mechanical energy to move a vehicle). Conversely, work can also be done on a system, leading to changes in internal energy, which can result in heating of the system.

This interplay emphasizes that while heat and work may manifest differently, they are fundamentally linked through the conservation of energy. Understanding this relationship is crucial in thermodynamics, as it allows for the calculation and prediction of energy transformations in various processes.