I want to know the answer to the following question:
What states that the system doing work always loses some energy as waste heat?
All the background I'm provided with is that "For "closed systems" with no external source or sink of energy, the first law of thermodynamics states that a system's energy is constant unless energy is transferred in or out by mechanical work or heat, and that no energy is lost in transfer.". Is that enough to answer the question?
Answer: no