Mnemonic 1: Four Spontaneity Cases — "Exo-Plus Always, Endo-Minus Never"

• $\Delta H(-)$ + $\Delta S(+)$ = ALWAYS spontaneous ("Exo-Plus Always")
• $\Delta H(+)$ + $\Delta S(-)$ = NEVER spontaneous ("Endo-Minus Never")
• $\Delta H(-)$ + $\Delta S(-)$ → LOW T wins ("Cold helps Exo")
• $\Delta H(+)$ + $\Delta S(+)$ → HIGH T wins ("Hot helps Endo")

Mnemonic 2: Process Types — "ISO-ADIA: T-A-V-P"

• ISOthermal → constant Temperature ($\Delta U = 0$)
• ADIAbatic → Absolutely no heat ($q = 0$)
• Isochoric → constant Volume ($w = 0$)
• Isobaric → constant Pressure ($q = \Delta H$)

Mnemonic 3: Sign Convention — "W-ON positive, Q-IN positive"

Work done ON system = positive. Heat flowing IN to system = positive.

Mnemonic 4: Heat Capacities — "3-5-7-9 for 1-2-3 atoms"

• Monoatomic: $C_v = \frac{3R}{2}$ (3 DOF)
• Diatomic: $C_v = \frac{5R}{2}$ (5 DOF)
• Triatomic linear: $C_v = \frac{7R}{2}$ (7 DOF)
• Always add $R$ to get $C_p$: "Add R to get $C_p$"

Mnemonic 5: Enthalpy Signs — "BIG = BIG negative"

• Bond dissociation: Always + (Big energy input needed)
• Ionization: Always + (Input energy needed)
• Group 1 electron affinity: Can be $-$ (Groups 17 strongly $-$)
• Combustion and Lattice: Always $-$ (Bonds/ions form)

Mnemonic 6: $\Delta G^\circ$ and K Relationship

$K > 1$ → products favored → $\ln K > 0$ → $-RT\ln K < 0$ → $\Delta G^\circ < 0$ "BIG K → Negative G"