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First Law of Thermodynamics definitions

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  • First Law of Thermodynamics
    A principle stating that energy is conserved and only changes form or location between a system and its surroundings.
  • Energy Transfer
    The movement of energy between a chemical reaction or substance and everything else, often as heat or work.
  • System
    The specific substance or chemical reaction under observation, isolated from everything else for study.
  • Surroundings
    All matter and energy outside the system, including containers, air, and the universe.
  • Heat
    The flow of thermal energy from a region of higher temperature to one of lower temperature, symbolized by q.
  • Work
    The energy transfer resulting from movement against an opposing force or gravity, represented by w.
  • Thermal Energy
    The internal energy associated with the temperature of a substance, responsible for heat flow.
  • Sign Convention
    The rule assigning positive or negative values to heat and work, depending on energy flow direction.
  • Negative q
    Indicates the system is losing heat to its surroundings, such as when a reaction releases energy.
  • Positive q
    Indicates the system is gaining heat from its surroundings, such as when a reaction absorbs energy.
  • Negative w
    Represents the system performing work on the surroundings, like gas expanding against a piston.
  • Positive w
    Represents the surroundings performing work on the system, such as compressing cases in a piston.
  • Opposing Force
    Any resistance, such as gravity or pressure, that must be overcome for work to be done.
  • Chemical Reaction
    A process involving the transformation of substances, often studied as the system in thermodynamics.