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First Law of Thermodynamics quiz

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Terms in this set (15)

  • What does the first law of thermodynamics state about energy?
    The first law states that energy cannot be created or destroyed, only transferred or transformed.
  • What is meant by the conservation of energy in the context of the first law of thermodynamics?
    Conservation of energy means the total energy in a system and its surroundings remains constant; energy is only transferred between them.
  • What are the three types of systems discussed in thermodynamics?
    The three types are open systems (transfer matter and energy), isolated systems (no transfer), and closed systems (transfer only energy).
  • Which type of system is most relevant to the first law of thermodynamics?
    The closed system is most relevant because it involves only the transfer of energy, not matter.
  • What happens if a system gains 100 joules of energy according to the first law?
    The surroundings must lose 100 joules of energy, keeping the total energy constant.
  • What does the variable 'q' represent in thermodynamics?
    The variable 'q' represents heat exchanged between the system and surroundings.
  • What does delta U (or delta E) represent in a chemical reaction?
    Delta U (or delta E) represents the change in internal energy of the system.
  • What is the equation relating internal energy, heat, and work?
    The equation is delta U = Q + W, where Q is heat and W is work.
  • Under constant pressure, what is q equal to?
    Under constant pressure, q is equal to delta H, which is the enthalpy change.
  • How is work (W) calculated in thermodynamics?
    Work is calculated as W = -PΔV, where P is pressure and ΔV is the change in volume.
  • When is heat (q) positive for a system?
    Heat is positive when the system absorbs or gains energy from the surroundings.
  • When is heat (q) negative for a system?
    Heat is negative when the system releases or loses energy to the surroundings.
  • When is work (W) positive for a system?
    Work is positive when work is done on the system by the surroundings, such as compressing a gas.
  • When is work (W) negative for a system?
    Work is negative when the system does work on the surroundings, such as expanding against a piston.
  • How does the first law of thermodynamics relate to changes in volume and heat in a gas system?
    Absorbing or releasing heat can cause gas molecules to change volume, which is connected to work done by or on the system.