Track heat-like energy changes at constant pressure.
Bond making, phase change and reaction energetics contribute to enthalpy changes.
Side 152
Physical Chemistry
Chemical behavior explained with physical laws: energy determines feasibility, kinetics determines rate, quantum structure shapes bonding, and statistics connects molecules to bulk matter.
state→energy→molecular structure→rate→observation
04lenses
16working concepts
V0content
SS-1.0standard
Chemical change is constrained by energy and entropy.
State functions organize equilibrium and spontaneity without specifying how quickly a process occurs.
Measure the thermodynamic state variable associated with multiplicity and dispersal.
Entropy participates with enthalpy in determining free-energy change.
Combine energetic and entropic terms at fixed temperature and pressure.
Negative reaction Gibbs energy favors forward change under specified conditions.
Measure how free energy changes with composition.
Equilibrium is expressed through balanced chemical potentials across components and phases.
Reaction rates depend on pathways and barriers.
A thermodynamically favorable reaction can still be extremely slow.
Relate reaction rate to concentrations.
Experimental rate laws reveal kinetic structure that stoichiometry alone does not determine.
Control how rapidly trajectories reach products.
Higher barriers suppress rate even when products are thermodynamically favored.
Decompose overall change into elementary steps.
The slow or kinetically controlling steps shape the observed rate law.
Lower barriers through an alternative path.
Catalysts alter rate without changing equilibrium thermodynamics.
Electronic structure determines molecular energy levels and bonding.
Quantum mechanics supplies the microscopic states that chemistry uses.
Represent quantum state amplitudes.
Observable probabilities are derived from the state rather than from classical trajectories.
Describe one-electron spatial structure in an approximation.
Orbital shape and energy help explain bonding and spectroscopy.
Allow only particular energy levels.
Discrete transitions generate characteristic spectral lines.
Combine atomic orbitals across a molecule.
Bonding and antibonding occupancy help explain bond order and electronic behavior.
Macroscopic chemistry emerges from ensembles of molecular states.
Statistical mechanics and spectroscopy connect microscopic populations to measurable bulk properties.
Weight states by energy and temperature.
Higher temperatures spread population across more excited states.
Summarize accessible molecular states.
Thermodynamic quantities can be derived from this statistical object.
Probe transitions with electromagnetic radiation.
Different frequency ranges reveal rotational, vibrational or electronic structure.
Encode environment and dynamics in spectra.
Broadening and splitting can report collisions, fields and molecular interactions.
Feasible is not the same as fast. Physical chemistry separates thermodynamic driving force from kinetic pathway and then connects both to molecular structure.