Thermodynamics Cheat Sheet

Key Definitions

• Thermodynamics: Study of heat, work, and energy transformations.

• System: Part of the universe being studied (open, closed, isolated).

• Surroundings: Everything outside the system.

• Heat (Q): Energy transferred due to temperature difference.

• Work (W): Energy transferred when a force acts over a distance.

Important Concepts

Laws of Thermodynamics

• Zeroth Law: If A is in equilibrium with B, and B with C, then A is in equilibrium with C. ✅

• First Law: Energy cannot be created or destroyed, only transformed. ΔU = Q - W ✅

• Second Law: Total entropy of an isolated system can never decrease. ✅

• Third Law: As temperature approaches absolute zero, entropy approaches a constant minimum. ✅

Types of Processes

• Isothermal: Constant temperature (Q = W).

• Adiabatic: No heat exchange (Q = 0).

• Isobaric: Constant pressure (W = PΔV).

• Isochoric: Constant volume (W = 0).

Key Formulas

• ΔU: Change in internal energy

• Q: Heat added to the system

• W: Work done by the system

W = PΔV ✅

• P: Pressure

• ΔV: Change in volume

S = k ln(Ω) ✅

• S: Entropy

• k: Boltzmann constant

• Ω: Number of microstates

Common Mistakes to Avoid

Common Mistake: Confusing heat with temperature; heat is energy, temperature is a measure of thermal energy.

Memory Tricks

Tip: "K.E.T." — Kinetic energy, Energy conservation, Thermodynamics laws.

Key Diagrams

     +-----------------+
     |                 |  
     |      System     |  
     |                 |  
     +-----------------+
         |         |
         |         |
     Heat/Q     Work/W
         |         |
         v         v
     +-----------------+
     |   Surroundings   |
     +-----------------+

Tip: Ensure clarity on system types and process characteristics for exam questions.