Section 1 review
Thermodynamics is the field of physics studying how thermal energy can be converted to or from other forms of energy, usually mechanical or electrical energy. The steam engine is an example of a thermodynamic system, where heat drives a shaft to pump water or power a train. The laws of thermodynamics describe the physics behind thermodynamic processes such as the steam engine. The zeroth law implies that no heat will flow between two objects at the same temperature, which means that the two are in thermal equilibrium with each other. The first law is a thermodynamic restatement of energy conservation, where the change in energy of a system equals the heat added to it and the work done on it. The second law states that entropy cannot decrease for any naturally occurring process. This law implies that, when heat is transferred in a thermodynamic process, the process is not reversible. Heat spontaneously flows from hotter objects to colder ones, but the reverse never occurs. The third law states that absolute zero is the minimum possible temperature and the temperature at which the entropy of a system also drops to its minimum. Read the text aloud
thermodynamics, zeroth law of thermodynamics, first law of thermodynamics, entropy, second law of thermodynamics, reversibility, third law of thermodynamics

ΔE=Q+W
ΔS0

Review problems and questions

  1. Jean wants to build a machine that has a wheel that will never stop turning. She claims that it will work because energy is conserved. Is Jean right? Use the first law of thermodynamics to explain. Read the text aloud Show
  1. When a container of gas expands, is positive work done on the gas or is the gas doing positive work on the surroundings? Read the text aloud Show
  1. Kaleb fills a glass with half lemon-lime soda and half root beer. The two drinks mix together. Explain why Kaleb’s drinks will not naturally separate themselves from one another after being mixed. Read the text aloud Show
  1. After learning Newton’s first law, Natasha figures that if she gets her car up to the speed she wants, it will continue moving at that speed until she applies the brakes. When she performs an experiment to test this, however, her car slows down and eventually stops without her pressing the brakes. When she gets out to examine her car, she notices that the tires are warm. What happened? Read the text aloud Show
  1. Match each statement below to the corresponding law of thermodynamics.
    1. No engine can be 100% efficient.
    2. A system can only have zero entropy if it is cooled to absolute zero (0 K).
    3. Energy is conserved in thermodynamic systems.
    4. If A and B are at the same temperature, and B and C are at the same temperature, then A and C must also be at the same temperature. Read the text aloud Show
  1. Simon received several balloons filled with pure nitrogen gas for his birthday. He left them in his room for a couple days, and they all deflated. Will the nitrogen gas that escaped ever separate itself from the other gas in his room? Read the text aloud Show

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