Question

1. which is a consequence of the third law of thermodynamics? (1 point)

energy is not always conserved.
heat engines are less than 100 percent efficient.
engines produce more waste heat than work.
engines cannot discharge waste heat.

Explanation:

1. Analyze the first option: The first law of thermodynamics states energy is conserved, so "Energy is not always conserved" is incorrect.
2. Analyze the second option: The third law of thermodynamics relates to the concept of absolute zero and the entropy of a perfect crystal. However, the fact that heat engines are less than 100% efficient is related to the second law (Carnot's theorem), but wait, no—wait, actually, the second law (and related concepts) lead to heat engines having less than 100% efficiency. Wait, maybe I made a mistake. Wait, the third law is about entropy at absolute zero. Wait, let's re - evaluate. Wait, the options:

• "Heat engines are less than 100 percent efficient" is a consequence of the second law (Carnot cycle shows that efficiency $\eta=1 - \frac{T_C}{T_H}$, so it's less than 1). But maybe the question has a mix - up? Wait, no, let's check the other options.
• "Engines produce more waste heat than work": This is not a direct consequence of the third law.
• "Engines cannot discharge waste heat": This is false, engines do discharge waste heat.
• Wait, maybe the question's options have a mis - association, but among the options, "Heat engines are less than 100 percent efficient" is the only one that is a valid thermodynamic consequence (even if it's more related to the second law, but maybe the question has a typo). Or maybe I misremember. Wait, the third law: the entropy of a perfect crystalline substance at absolute zero temperature is zero. But how does that relate to heat engines? Wait, no, maybe the options are wrong, but among the given options, "Heat engines are less than 100 percent efficient" is the correct statement about thermodynamic efficiency, which is a key thermodynamic concept. The other options are incorrect: energy is conserved (first law), engines do produce work and waste heat (the ratio depends on the engine, not that waste heat is always more), and engines can discharge waste heat. So the correct option is "Heat engines are less than 100 percent efficient".

Answer:

Heat engines are less than 100 percent efficient.