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The Zeroth, First, Second, and Third Laws of Thermodynamics

Precise statements, mathematical formulations, and practical implications of each of the four laws of thermodynamics for physics and chemistry students.

9 cards· by GuruOwl

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  1. 01
    The zeroth law of thermodynamics states that if two systems are each in thermal equilibrium with a third system, they are in thermal equilibrium with each other.
    This transitive property provides the basis for the definition of temperature and the use of thermometers.
    Flashify::Thermodynamics::ZerothLaw
  2. 02
    The first law of thermodynamics is a statement of the conservation of energy.
    It implies that energy cannot be created or destroyed, only transformed.
    Flashify::Thermodynamics::FirstLaw
  3. 03
    In the physics convention for a closed system, the change in internal energy is expressed as ΔU = Q − W.
    Q is heat added to the system and W is work done by the system.
    Flashify::Thermodynamics::FirstLaw
  4. 04
    Contrast internal energy (U) with heat (Q) and work (W) regarding path dependency.
    Internal energy is a state function (path-independent), while heat and work are path-dependent.
    State functions depend only on the current state of the system, not how it reached that state.
    Flashify::Thermodynamics::StateFunctions
  5. 05
    The second law of thermodynamics states that the entropy of an isolated system or the universe never decreases.
    ΔS_universe ≥ 0 for any real process; equality holds only for reversible processes.
    Flashify::Thermodynamics::SecondLaw
  6. 06
    The maximum efficiency of a Carnot engine is calculated as 1 − (TC/TH).
    This demonstrates that no heat engine can be 100% efficient as long as TC > 0.
    Flashify::Thermodynamics::SecondLaw
  7. 07
    The third law of thermodynamics states that the entropy of a perfect crystal at absolute zero (0 K) is zero.
    This law implies that absolute zero is unattainable in a finite number of steps.
    Flashify::Thermodynamics::ThirdLaw
  8. 08
    In statistical mechanics, the Boltzmann formula for entropy is S = k ln W.
    W represents the number of microstates consistent with a given macrostate.
    Flashify::Thermodynamics::StatisticalMechanics
  9. 09
    How do biological systems decrease local entropy without violating the second law?
    They increase the entropy of their surroundings by a greater amount.
    The total entropy of the universe still increases, satisfying ΔS_universe ≥ 0.
    Flashify::Thermodynamics::Biology