🔹 Thermodynamic system: A finite part of the universe under observation.
Boundaries can be real/imaginary. Types: open (mass & energy transfer), closed (only energy), isolated (no transfer).
🔹 Surroundings: Everything outside the system. System + surroundings = universe.
🔹 State function: Property that depends only on current state, not path taken. Examples: Pressure (P), Volume (V), Temperature (T), Internal energy (U), Enthalpy (H), Entropy (S).
Work (W) & heat (Q) are NOT state functions; they are path functions.
Internal energy U: state function; ΔU = Q + W (first law). Q & W individually path dependent but ΔU independent.
🧠 State functions (PVT UHS): “Public Very Tasty U-Haul Service” – P (pressure), V (volume), T (temp), U (int. energy), H (enthalpy), S (entropy).
🧠 Not state functions: “QWERTY” – Q (heat) & W (work) are path functions (like typing path on keyboard).
🧠 Open/closed/isolated: “OCEAN” – Open: Coffee cup (mass & heat) ; Closed: sealed flask (only energy) ; Isolated: thermos (ideally nothing).
📌 TIP: State functions are exact differentials (dU, dH) while work/heat are inexact (đQ, đW).
📌 MDCAT TRICK: In MCQ, if you see “depends on path” → work/heat; if “initial & final only” → state function.
GUIDELINES: Draw boundary around system in every problem. Identify transfer. For state fn: just look at start/end, ignore how you got there. Practice 10 MCQs below.
Master thermodynamics in 4 days: