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First Law of Thermodynamics quiz

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  • What does the first law of thermodynamics state about energy?
    It states that energy cannot be created or destroyed, only transferred between a system and its surroundings.
  • In chemistry, what is typically considered the 'system'?
    The system is the substance or chemical reaction being studied or analyzed.
  • What are the 'surroundings' in a thermodynamic context?
    The surroundings include everything that is not part of the system, such as the container and the external environment.
  • What are the two main ways energy can be transferred between a system and its surroundings?
    Energy can be transferred as heat (q) or as work (w).
  • How is heat (q) defined in thermodynamics?
    Heat is the flow of thermal energy from a higher temperature object to a lower temperature object.
  • What does work (w) represent in thermodynamics?
    Work is the movement of reacting molecules against gravity or an opposing force.
  • When is the sign of q (heat) positive for a system?
    The sign of q is positive when the system gains, absorbs, or takes in heat.
  • When is the sign of q (heat) negative for a system?
    The sign of q is negative when the system loses, evolves, releases, or gives off heat.
  • When is the sign of w (work) negative for a system?
    The sign of w is negative when the system does work on the surroundings.
  • When is the sign of w (work) positive for a system?
    The sign of w is positive when the surroundings do work on the system.
  • If gas molecules push up against a piston, what is the sign of w and why?
    The sign of w is negative because the system (gas) is doing work on the surroundings (piston).
  • If a piston is pushed down by an outside force onto gas molecules, what is the sign of w?
    The sign of w is positive because the surroundings are doing work on the system.
  • What happens to energy when it is transferred between system and surroundings?
    Energy changes from one form to another but is not created or destroyed.
  • In the context of heat transfer, which direction does heat naturally flow?
    Heat naturally flows from a hotter object to a colder object.
  • How do you determine the sign of q for a system during a heat transfer?
    If the system gains heat, q is positive; if it loses heat, q is negative.