Entropy and Second Law of Thermodynamics - AP Physics 2

S. Standard symbol used to represent entropy in thermodynamic equations.

Entropy becomes constant at absolute zero. All substances reach minimum entropy at absolute zero temperature.

Higher entropy means greater energy dispersal. Energy spreads out more uniformly with increasing entropy.

Entropy increases or remains constant. Second Law prevents entropy decrease in isolated systems.

Disorder or randomness. Quantifies the degree of molecular chaos or energy spread.

$\Delta S = 2 , J/K$. Using $\Delta S = Q/T = 150/75 = 2$ J/K.

Number of microstates. Represents the total number of possible microscopic arrangements.

$\Delta S = 1.67 , J/K$. Using $\Delta S = Q/T = 500/300 = 1.67$ J/K.

Entropy is a measure of a system's disorder. Entropy quantifies the randomness or energy dispersal in a system.

Entropy increases. Mixing creates more possible molecular arrangements and disorder.

Increased disorder in the system. Positive $\Delta S$ means more microstates and greater randomness.

$\Delta S = \frac{\Delta H}{T}$. Enthalpy change divided by temperature during phase changes.

$\Delta S = \frac{Q}{T}$. Heat $Q$ divided by temperature $T$ gives entropy change.

Entropy of an isolated system never decreases. This fundamental law states entropy never decreases in isolated systems.

Decreased disorder or energy dispersal. Negative $\Delta S$ means the system becomes more ordered.

Total entropy change is zero. No net entropy increase means the process is reversible.

Positive. Spontaneous processes always increase total system entropy.

S. Standard symbol used to represent entropy in thermodynamic equations.

Second Law of Thermodynamics. Entropy increase limits the conversion of heat to work.

Reactions tend to increase total entropy. Reactions favored when they increase overall system entropy.

Joules per Kelvin (J/K). Energy per temperature unit in the International System of Units.

Entropy maximizes, leading to uniform energy distribution. Maximum entropy means complete thermal equilibrium throughout the universe.

They are impossible. Entropy increase prevents 100% efficient energy conversion.

Entropy increases with temperature. Higher temperatures allow more molecular motion and disorder.

$\Delta S = 0$. No heat transfer means no entropy change in ideal case.

Second Law of Thermodynamics. Entropy increase determines which processes occur naturally.

A specific configuration of a system's particles. One possible arrangement of all particles in the system.

Boltzmann's constant. Fundamental physical constant linking microscopic and macroscopic properties.

Reversible process. Only reversible processes maintain constant total entropy.