G. Watson Student_Notes AP Chem Unit 6

Thermochemistry

The study of the heat energy associated with chemical reactions and physical changes.

Endothermic Reaction

A reaction that absorbs energy from its surroundings, resulting in a positive enthalpy change (∆H > 0).

Exothermic Reaction

A reaction that releases energy to its surroundings, resulting in a negative enthalpy change (∆H < 0).

Enthalpy (H)

A thermodynamic quantity that represents the total heat content of a system.

Heat Transfer (q)

The amount of energy transferred as heat during a temperature change; calculated using q = c m ∆T.

Calorimetry

The measurement of heat changes in physical and chemical processes using a calorimeter.

Heat Capacity (C)

The amount of heat required to raise the temperature of a substance by 1 degree Celsius.

Specific Heat Capacity (c)

The amount of heat required to raise the temperature of 1 gram of a substance by 1 degree Celsius.

Thermal Equilibrium

A state in which two objects in thermal contact reach the same temperature.

Bond Enthalpy

The energy required to break one mole of a particular type of bond in gaseous molecules, measured in kJ/mol.

Molar Enthalpy of Formation

The heat change that results when one mole of a compound is formed from its elements in their standard states.

Hess’s Law

The principle stating that the total enthalpy change for a reaction is the same, regardless of the number of steps in the reaction.

Latent Heat

The heat required for a phase change, such as melting or vaporization, at constant temperature.

Heat of Vaporization

The amount of energy needed to convert a liquid into a gas at its boiling point.

Heat of Fusion

The amount of heat required to turn a solid into a liquid at its melting point.

Kinetic Energy (KE)

The energy that an object possesses due to its motion, quantified as KE = ½mv².

Potential Energy (PE)

The energy stored in an object due to its position or configuration.

Thermal Energy

The total energy of the particles in a substance, related to temperature.

Enthalpy Change (∆H)

The difference in enthalpy between products and reactants during a chemical reaction.

Phase Change

A transition of matter from one state to another, such as from solid to liquid.