PHY3513 – Heat and Thermodynamics is a 3-credit upper-division physics course on thermal physics: classical thermodynamics from the fundamental postulates through entropy, equations of state, thermodynamic potentials, Maxwell relations, and phase transitions, with an introduction to statistical mechanics at most institutions. It appears in catalogs as "Heat and Thermodynamics," "Thermal Physics" (the University of Florida), and "Thermodynamics" (Florida International University).
Thermodynamics occupies an unusual position among physical theories. It is macroscopic and phenomenological — it makes no assumption about atoms, and its laws were established before atomic theory was settled — which is precisely why it has outlasted the theories that were supposed to replace it. Einstein's remark that thermodynamics is the only physical theory of universal content he was convinced would never be overthrown is quoted in most textbooks for good reason.
Content covers fundamental concepts — systems, states, equilibrium, and the zeroth law; temperature — thermometry and the absolute scale; equations of state — ideal gas, van der Waals, and real gases; work and heat — path dependence and the distinction between them; the first law — internal energy, and its application to processes; heat capacity and calorimetry; the second law — its statements, the Carnot cycle, and heat engines and refrigerators; entropy — definition, calculation, the Clausius inequality, and irreversibility; the third law; thermodynamic potentials — enthalpy, Helmholtz and Gibbs free energy, and Legendre transformations; Maxwell relations and the mathematical machinery of thermodynamics; phase transitions — the Clausius-Clapeyron relation, critical points, and classification; chemical potential and open systems; kinetic theory — the Maxwell-Boltzmann distribution, transport, and equipartition; and introductory statistical mechanics — microstates, the Boltzmann factor, and partition functions.
Offered at Florida universities with physics programs.
Florida's physics-adjacent employment concentrates in aerospace and defense along the Space Coast and in the Panhandle, photonics and optics in Central Florida, semiconductor and materials work, energy utilities, and the state's research universities and national-lab-affiliated facilities including the National High Magnetic Field Laboratory in Tallahassee.
The single most useful warning about this course. Students expecting conceptual difficulty are often surprised that the physics ideas are relatively few — four laws, some potentials, entropy — while the mathematical manipulation is relentless. Thermodynamics is largely an exercise in partial derivatives: which variables are held constant, how to change variables, how to derive one relation from another.
Prerequisites reflect this. The University of Florida and Florida International both require PHY2049 (calculus-based physics II) and MAC2313 (Calculus III / multivariable calculus), often as a corequisite — and multivariable calculus is used extensively rather than occasionally. A student shaky on partial derivatives, the chain rule for functions of several variables, and exact versus inexact differentials will spend the term fighting the mathematics rather than learning the physics.
The practical remedy is to review multivariable calculus before the term starts, specifically partial derivatives, the cyclic and reciprocal relations, and total differentials. That investment pays for itself in the first three weeks.
The idea students find hardest, partly because it is taught twice in different languages. The thermodynamic definition arrives first — entropy change as heat transferred reversibly divided by temperature — and is operational but unilluminating. The statistical definition arrives later — entropy as a measure of the number of accessible microstates — and is illuminating but initially seems unrelated.
The course's real intellectual work is connecting them: understanding why counting microstates produces a quantity that behaves exactly like the macroscopic entropy, and why the second law is a statement about overwhelming probability rather than an absolute prohibition. Students who reach that connection understand thermodynamics; students who keep the two definitions in separate compartments can pass exams and remain confused.
Worth avoiding the popular shorthand: entropy is not "disorder." That analogy misleads more than it helps — it fails for many real systems, and it obscures the actual content, which is about multiplicity of microstates. Schroeder's text is particularly good on this and is worth reading even if another book is assigned.
The standard advice for upper-division physics, and it applies with unusual force here because the difficulty is procedural. Reading a worked derivation produces a feeling of understanding that does not transfer to an exam. The skills being built — recognizing which potential to use, choosing variables, deploying a Maxwell relation to convert an unmeasurable derivative into a measurable one — are pattern recognition acquired only through repetition.
What works: attempt every problem before looking at any solution; when stuck, identify precisely where you are stuck rather than reading the whole solution; redo problems you got wrong a week later; and work with others, because explaining a derivation aloud exposes gaps that silent reading conceals. Departmental old exams are the best available predictor of what will be asked.
Worth understanding as curricular context. PHY3513 typically pairs with or precedes a second course (PHY4523 statistical physics at several Florida institutions), and together they form the thermal and statistical physics sequence that graduate programs assume and that physics GRE and qualifying examinations test.
The statistical mechanics content also has unexpected reach. Partition functions, the Boltzmann distribution, and the notion of maximizing entropy subject to constraints appear directly in machine learning (Boltzmann machines, softmax, maximum-entropy models), in information theory, in chemistry, and in quantitative finance — which is part of why physics graduates are recruited into those fields. A student who intends to leave physics after the bachelor's should still take this material seriously for that reason.
Worth noticing, because the abstraction can feel disconnected. Engine and refrigerator efficiency limits, why a heat pump beats resistive heating, why the Carnot bound cannot be engineered around, phase diagrams in materials science, protein folding and molecular motors in biophysics, stellar structure and black hole thermodynamics in astrophysics, atmospheric stability in meteorology, and battery and fuel cell chemistry all rest on this course.
Florida-specific relevance is real too: aerospace propulsion on the Space Coast, HVAC and building energy in a cooling-dominated climate, and atmospheric thermodynamics underlying the convection and hurricane physics that define the state's weather. Students who connect the formalism to a concrete system they care about retain it far better.
The same SCNS number carries different titles: "Heat and Thermodynamics," "Thermal Physics" (University of Florida), and "Thermodynamics" (Florida International University), all at 3 credits and all lecture-only — there is no laboratory component, which distinguishes it from the lower-division PHY2048C/PHY2049C sequence and from PHY3101C Modern Physics. Prerequisites are PHY2049 or equivalent and MAC2313, sometimes as a corequisite. SCNS equivalency applies to the same number at the same level, never across numbers; because this is a 3000-level major course, transfer students should confirm the receiving physics department accepts it toward the major, since some require upper-division major coursework in residence.
Generated September 1, 2026 · Updated September 1, 2026