Thermodynamics Concepts

Flashcards summarizing key terms and definitions from the thermodynamics lecture notes.

System

Part of the universe we wish to study, a particular reaction.

Surroundings

All other parts of the universe, including the reaction vessel.

Exothermic Reaction (ΔH < 0)

A reaction that releases heat and tends to occur spontaneously.

Endothermic Reaction (ΔH > 0)

A reaction that absorbs heat and does not tend to occur spontaneously.

Entropy (S)

A measure of disorder or randomness in a system.

First Law of Thermodynamics

Energy cannot be created or destroyed, only transformed.

Second Law of Thermodynamics

The entropy of the universe always increases in a spontaneous process.

Third Law of Thermodynamics

The entropy of a perfect crystalline substance is zero at absolute zero (0 K).

Gibbs Free Energy (G)

A measure of the spontaneity of a reaction and the useful energy available from it.

Spontaneous Process

A process that occurs without a continuous input of energy from an outside system.

Nonspontaneous Process

A process that occurs only if the surroundings continuously supply energy.

Absolute Entropy (S°)

The entropy of a substance at a standard state (25 °C, 1 atm, or 1.0 M for solutions).

Standard Entropy

Defined at standard conditions; measured in J/(mol K).

Energy Diagram

A graphical representation of the energy changes during a chemical reaction.

Equilibrium Condition

Occurs when the rate of the forward reaction equals the rate of the reverse reaction.

Crossover Temperature

The temperature at which a reaction changes from non-spontaneous to spontaneous.