Energy can be transferred without doing work, primarily through heat, as explained in thermodynamics. The concept of entropy plays a crucial role in understanding why some energy becomes unavailable for work due to irreversibilities in systems. In chemical reactions, unavailable energy arises from these irreversibilities, leading to an increase in entropy. The relationship between entropy and Gibbs free energy indicates that while entropy represents unavailable energy, it also affects the energy available to do work. Understanding these principles clarifies the complex interactions between energy transfer, work, and entropy.