Phase Transitions and Thermodynamics

These flashcards cover key concepts in thermodynamics and phase transitions discussed in Lecture 4, focusing on definitions and important principles related to physical chemistry.

Phase Transition

A change of a substance from one state (solid, liquid, gas) to another.

Boiling Point

The temperature at which a liquid's vapor pressure equals the external pressure, allowing it to transition to a gas.

Dynamic Equilibrium

A condition in which evaporation and condensation occur at the same rate, resulting in stable vapor pressure.

Vapor Pressure

The partial pressure of the vapor over a liquid at equilibrium; increases as temperature rises.

Enthalpy of Fusion (ΔHfus)

The heat absorbed when a solid becomes a liquid at constant temperature and pressure, for water it is 6.01 kJ/mol.

Enthalpy of Vaporization (ΔHvap)

The heat required to convert a liquid into a gas at constant temperature and pressure, for water it is 40.7 kJ/mol.

Allotropes

Different forms of an element in the same physical state, e.g., carbon can exist as graphite or diamond.

Ionic Bond

A bond formed by the electrostatic attraction between positively and negatively charged ions.

Covalent Bond

A bond formed between atoms by the sharing of a pair of electrons.

Bond Enthalpy

The average enthalpy change for breaking a bond in a molecule in the gas phase, indicating bond strength.

Lattice Energy

The change in energy when an ionic solid separates into gas-phase ions; used to compare ionic bond strength.

Ionization Energy

The energy required to remove an electron from an atom or ion.

Electron Affinity

The energy change that occurs when an electron is added to a neutral atom, often releasing energy.

Coulomb’s Law

Describes the electrostatic interaction between charged particles; states that the force is proportional to the product of the charges and inversely proportional to the distance between them.

Extensive State Function

A property that depends on the amount of substance (e.g., enthalpy, volume).

First Law of Thermodynamics

States that energy cannot be created or destroyed, only transformed; also called the Law of Energy Conservation.

Second Law of Thermodynamics

States that the total entropy of an isolated system can never decrease over time, leading to the concept of spontaneous processes.