Key Concepts: Enthalpy Entropy Free Energy

Core Definitions

• Enthalpy (H): The total heat content of a system. ΔH < 0 = exothermic; ΔH > 0 = endothermic.
• Entropy (S): A measure of disorder/randomness. ΔS > 0 means disorder increases.
• Gibbs Free Energy (G): ΔG = ΔH − TΔS. If ΔG < 0, the reaction is spontaneous.
• Spontaneous Reaction: Occurs without continuous outside energy input (ΔG < 0).