Depend only on the current state.
Internal energy and entropy are state functions; heat and work are path-dependent transfers.
Side 143
Thermodynamics
A macroscopic theory of energy, heat, work and irreversibility that constrains what physical and engineered processes can accomplish regardless of microscopic detail.
state→energy→process→entropy→limit
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16working concepts
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SS-1.0standard
A thermodynamic state is described by macroscopic variables.
Temperature, pressure, volume and composition summarize enormous numbers of microscopic degrees of freedom.
Relate measurable state variables.
Ideal-gas behavior is a useful approximation with known limits.
Remove macroscopic driving gradients.
Equilibrium defines reference states even when many real systems operate far from it.
Distinct states of matter occupy different stability regions.
Phase boundaries depend on temperature, pressure and composition.
Energy is conserved while crossing system boundaries as heat or work.
The first law is bookkeeping with physical consequences.
Choose what is inside the analysis boundary.
Closed, open and isolated systems require different accounting.
Transfer energy because of temperature difference.
Heat is energy in transit, not a substance contained in a body.
Transfer energy through generalized forces and displacements.
Mechanical, electrical and other work modes can change system energy.
Store microscopic energy within the system.
Changes in internal energy balance net heat and work transfer.
Not all energy conversions are equally possible.
Entropy introduces directionality and limits on converting heat into useful work.
Track dispersal and multiplicity through a state variable.
For an isolated system, total entropy does not decrease.
Define the ideal limit of zero entropy production.
Real finite-rate processes generate entropy through friction, mixing and gradients.
Measure maximum useful work relative to an environment.
Exergy is destroyed by irreversibility even though total energy is conserved.
Thermodynamic irreversibility gives macroscopic time direction.
The connection to microscopic reversibility depends on statistical assumptions and boundary conditions.
Engines and refrigerators convert energy within thermodynamic limits.
Cyclic devices reveal how state changes, heat reservoirs and work interact.
Convert part of heat input into work.
No cyclic engine can convert all absorbed heat into work while exchanging heat with reservoirs.
Set an upper efficiency bound from reservoir temperatures.
The bound is ideal and independent of working-fluid details.
Use work to move heat against a temperature gradient.
Performance is measured differently from heat-engine efficiency.
Include pressure loss, finite heat transfer and component inefficiency.
Engineering performance falls below reversible limits because real processes generate entropy.
Thermodynamics is a theory of constraints. It often tells you what cannot happen, how much work is fundamentally available and why real processes lose useful energy even before engineering details are considered.