Thermodynamics

50 lessons, pages 1716–1765.

  1. What Thermodynamics Describes — Energy changes, states and the limits of thermodynamic prediction
  2. System, Surroundings and Boundary — Defining the matter and energy included in a calculation
  3. Open, Closed and Isolated Systems — Classifying matter and energy exchange across a boundary
  4. State Functions and Path Functions — Why internal energy is state-dependent while heat and work depend on a route
  5. Heat and Work Sign Conventions — Tracking energy entering and leaving a chemical system
  6. Internal Energy and the First Law — Applying ΔU = q + w to a defined system
  7. Pressure-Volume Work — Using w = −PextΔV for expansion against constant external pressure
  8. Reversible Isothermal Gas Work — Integrating ideal-gas pressure for a quasistatic isothermal path
  9. Free Expansion and Path Dependence — Contrasting zero external-pressure work with other paths
  10. Ideal-Gas Internal Energy and Temperature — Relating ΔU to temperature change for an ideal gas
  11. Enthalpy as U + PV — Defining a state function useful for constant-pressure processes
  12. Heat at Constant Pressure and Volume — Conditions under which qp = ΔH and qv = ΔU
  13. Connecting Reaction ΔH and ΔU — Using gas-mole change for ideal-gas reactions
  14. Heat Capacity and Temperature Change — Relating supplied heat to a measured temperature rise
  15. Specific, Molar and Total Heat Capacity — Selecting mass, mole and sample-based heat-capacity units
  16. Calorimetry and Heat Balance — Equating heat lost and gained in an insulated measurement
  17. Bomb Calorimetry — Measuring combustion heat at approximately constant volume
  18. Coffee-Cup Calorimetry — Inferring solution-reaction enthalpy at near-constant pressure
  19. Thermochemical Equations — Scaling enthalpy with stoichiometric reaction extent
  20. Exothermic and Endothermic Profiles — Reading reaction-energy diagrams and ΔH signs
  21. Standard States and Standard Enthalpy — Reference pressure, pure substances and temperature reporting
  22. Standard Enthalpy of Formation — Forming one mole of compound from elements in standard states
  23. Reaction Enthalpy from Formation Data — Products-minus-reactants calculation with stoichiometric coefficients
  24. Enthalpy of Combustion — Complete oxidation of one mole of a stated fuel
  25. Enthalpy of Neutralisation — Acid-base heat and the common strong-acid strong-base net reaction
  26. Enthalpy of Solution and Dilution — Separating dissolution and subsequent concentration changes
  27. Enthalpy of Phase Changes — Fusion, vaporisation and sublimation as state-dependent energy changes
  28. Enthalpy of Atomisation — Producing gaseous atoms from an element in its reference state
  29. Bond Dissociation Enthalpy — Homolytic breaking of a specified gas-phase bond
  30. Average Bond Enthalpy Estimates — Broken-minus-formed bond sums and their approximation limits
  31. Hess's Law — Using state-function path independence to sum reaction enthalpies
  32. Reversing and Scaling Thermochemical Equations — Adjusting ΔH correctly when equations are manipulated
  33. Hess Calculations from Formation Reactions — Building target equations from standard formation steps
  34. Thermochemical Cycles — Constructing a closed enthalpy route with a known target
  35. Lattice Enthalpy Conventions — Distinguishing crystal formation from lattice dissociation signs
  36. Born-Haber Cycle Steps — Atomisation, ionisation, electron gain and crystal formation
  37. Calculating a Salt's Lattice Enthalpy — Solving a sodium-chloride Born-Haber energy balance
  38. Entropy and Energy Dispersal — Interpreting accessible arrangements without equating entropy to disorder
  39. Microstates and Boltzmann Entropy — Connecting multiplicity to S = kB ln Ω
  40. Standard Molar Entropy — Reading tabulated absolute entropy values and units
  41. Reaction Entropy from Standard Data — Products-minus-reactants calculation for ΔrS°
  42. Entropy Change of the Surroundings — Using −ΔHsys/T for an isothermal constant-pressure reservoir
  43. Second Law and Total Entropy — Testing spontaneous direction through system plus surroundings
  44. Gibbs Energy and Spontaneity — Applying ΔG = ΔH − TΔS at constant temperature and pressure
  45. Temperature Thresholds for ΔG — Finding when opposing enthalpy and entropy terms change sign
  46. Gibbs Energy Away from Standard Conditions — Using ΔG = ΔG° + RT ln Q for reaction direction
  47. Gibbs Energy and Equilibrium Constant — Interpreting ΔG° = −RT ln K without equating it to ΔG at equilibrium
  48. Coupled Processes and Feasibility — Summing Gibbs energy changes for linked reactions
  49. Mixed Thermodynamics Problems — Choosing heat, work, enthalpy or Gibbs methods from stated conditions
  50. Thermodynamics: Unit Review — Integrating the first law, Hess cycles, entropy and Gibbs energy