Thermochemistry Fundamentals

Thermochemistry

• Studies energy changes during chemical reactions and state changes.

Chemical Potential Energy

• Energy is stored in the bonds of chemical compounds.

Heat

• Energy transferred between objects due to temperature differences.

System

• A defined part of the universe focused on during analysis; can vary in size.

Law of Conservation of Energy

• Energy cannot be created or destroyed in chemical or physical processes.

Endothermic Process

• Absorbs heat from surroundings leading to a temperature drop in the environment.

Exothermic Process

• Releases heat into the surroundings, increasing external temperature.

Heat Capacity

• The amount of heat needed to increase an object's temperature by 1ºC.

Specific Heat

• The heat required to raise the temperature of 1 gram of a substance by 1ºC.

Calorimetry

• Technique for measuring heat flow into or out of a system during chemical and physical changes.

Calorimeter

• Insulated device designed to measure heat absorption or release.

Enthalpy (H)

• Represents the heat content of a system at constant pressure.

Thermochemical Equation

• A chemical equation that incorporates the enthalpy change associated with the reaction.

Heat of Reaction

• Enthalpy change for a specific chemical equation as written.

Heat of Combustion

• The enthalpy change associated with the complete burning of one mole of a substance.

Molar Heat of Fusion (∆Hfus)

• Heat absorbed to convert one mole of a solid into a liquid at a constant temperature.

Molar Heat of Solidification (∆Hsolid)

• Heat released when one mole of a liquid solidifies at a constant temperature.

Molar Heat of Condensation (∆Hcond)

• Heat released by one mole of vapor when it condenses into a liquid at constant temperature.

Molar Heat of Solution (∆Hsoln)

• Enthalpy change occurring during the dissolution of one mole of a substance.

Hess's Law of Heat Summation

• States that the total heat of reaction can be found by adding heats of individual reactions.

Standard Heat of Formation (ΔHf)

• Enthalpy change when forming one mole of a compound from its elements, measured under standard conditions (25°C).