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Activated Complex

A temporary, high-energy arrangement of atoms formed during a chemical reaction at the peak of the activation energy barrier

Capillary Action

The ability of a liquid to flow in narrow spaces without external forces due to adhesive and cohesive forces

Catalyst

A substance that increases the rate of a chemical reaction without being consumed in the process

Collision Theory

The theory that chemical reactions occur when particles collide with sufficient energy and proper orientation

Condensation

The phase change from gas to liquid

Critical Point

The temperature and pressure at which the distinction between liquid and gas phases disappears

Critical Pressure

The minimum pressure required to liquefy a gas at its critical temperature

Critical Temperature

The temperature above which a gas cannot be liquefied regardless of pressure applied

Deposition

The phase change from gas directly to solid without passing through the liquid phase

Enthalpy Change

The heat absorbed or released during a chemical or physical process at constant pressure

Enthalpy of Combustion

The heat released when one mole of a substance undergoes complete combustion with oxygen

Enthalpy of Reaction

The heat absorbed or released during a chemical reaction at constant pressure

Equilibrium

A state in which the forward and reverse reactions occur at equal rates and concentrations remain constant

Equilibrium Vapor Pressure

The pressure exerted by a vapor when it is in dynamic equilibrium with its liquid phase

Evaporation

The phase change from liquid to gas that occurs at the surface of a liquid below its boiling point

Freezing

The phase change from liquid to solid

Freezing Point

The temperature at which a liquid changes to a solid at a given pressure

Hess's Law

The principle that the total enthalpy change for a reaction is the same whether it occurs in one step or multiple steps

Intermediate

A species formed during a reaction mechanism that is produced in one step and consumed in another

Joule

The SI unit of energy equal to the work done when a force of one newton moves an object one meter

Melting

The phase change from solid to liquid

Melting Point

The temperature at which a solid changes to a liquid at a given pressure

Molar Enthalpy of Formation

The enthalpy change when one mole of a compound is formed from its elements in their standard states

Molar Enthalpy of Fusion

The amount of heat required to melt one mole of a solid at its melting point

Molar Enthalpy of Vaporization

The amount of heat required to vaporize one mole of a liquid at its boiling point

Phase

A physically distinct and homogeneous part of a system separated by boundaries

Phase Diagram

A graph showing the conditions of temperature and pressure at which different phases of a substance exist

Reaction Mechanism

The step-by-step sequence of elementary reactions by which an overall chemical reaction occurs

Specific Heat

The amount of heat required to raise the temperature of one gram of a substance by one degree Celsius

Sublimation

The phase change from solid directly to gas without passing through the liquid phase

Temperature

A measure of the average kinetic energy of particles in a substance

Thermochemical Equation

A balanced chemical equation that includes the enthalpy change for the reaction

Thermochemistry

The study of heat changes that occur during chemical reactions and physical processes

Triple Point

The temperature and pressure at which all three phases of a substance coexist in equilibrium

Unit Cell

The smallest repeating unit of a crystal lattice that shows the full symmetry of the structure

Vaporization

The phase change from liquid to gas

Volatile Liquids

Liquids that evaporate readily at room temperature due to high vapor pressure