Chapter 6 Thermochemistry Vocabulary

A comprehensive set of vocabulary flashcards covering fundamental thermodynamics and thermochemistry terms and equations from Chapter 6.

Thermochemistry

The study of energy changes that accompany chemical reactions.

Energy

The capacity to do work.

Work ($w$)

The result of an object being moved by a force, calculated as $w = F \times d$.

Heat ($q$)

The transfer of thermal energy between two objects that are at different temperatures.

Thermal Energy

The kinetic energy associated with the random motion of atoms and molecules.

Kinetic Energy

Energy available due to the motion of an object.

Potential Energy

Energy available due to the position of an object in a force field.

Chemical Energy

The form of energy stored within the structural units of chemical substances.

Joule ($J$)

The SI unit of energy, where $1\,J = 1\,kg \cdot m^2/s^2$.

System

The part of the universe that is of interest to us.

Surroundings

The remainder of the universe outside the system.

Open System

A system that can exchange both matter and energy with its surroundings.

Closed System

A system that can exchange energy, but not matter, with its surroundings.

Isolated System

A system that can exchange neither matter nor energy with its surroundings.

Thermodynamics

The study of all types of energy changes.

Law of Conservation of Energy

The principle that energy can neither be created nor destroyed and the total quantity of energy in the universe remains constant.

First Law of Thermodynamics

The total energy of the universe is constant, represented by the equation $\Delta E_{univ} = \Delta E_{sys} + \Delta E_{surr} = 0$.

Internal Energy ($E$)

The total energy possessed by a system, including thermal, chemical, and potential energies.

State of a System

The values of all pertinent macroscopic properties of the system.

State Function

A property that depends only on the current state of a system and not on the path used to reach that state.

Exothermic Process

A process in which the system releases heat to the surroundings.

Endothermic Process

A process in which the system absorbs heat from the surroundings.

Constant-Pressure Process

A process occurring at constant external pressure.

Enthalpy ($H$)

A thermodynamic quantity defined as $H = E + PV$.

Change in Enthalpy ($\Delta H$)

The heat absorbed or released during a constant-pressure process, calculated as $\Delta H = H_{final} - H_{initial}$.

Heat of Reaction ($\Delta H_{rxn}$)

The enthalpy change associated with a chemical reaction, calculated as $\Delta H_{rxn} = H_{products} - H_{reactants}$.

Thermochemical Equation

A balanced chemical equation that includes the associated enthalpy change.

Molar Enthalpy Change

The enthalpy change corresponding to one mole of reaction.

Calorimetry

The measurement of heat absorbed or released during a process.

Heat Capacity ($C$)

The amount of heat required to raise the temperature of a sample by one kelvin.

Molar Heat Capacity

The amount of heat required to raise the temperature of one mole of a substance by one kelvin.

Specific Heat Capacity ($c$)

The amount of heat required to raise the temperature of one gram of a substance by one kelvin.

Temperature Change ($\Delta T$)

The difference between final and initial temperature, $\Delta T = T_{final} - T_{initial}$.

Heat-Temperature Relationship

The formula used to calculate heat transfer: $q = C \Delta T$.

Bomb Calorimeter

A rigid, constant-volume calorimeter used primarily for combustion reactions.

Constant-Volume Calorimetry

Calorimetry performed under constant-volume conditions, where the measured heat corresponds to $\Delta E$.

Constant-Pressure Calorimetry

Calorimetry performed under constant-pressure conditions, where the measured heat corresponds to $\Delta H$.

Hess's Law of Heat Summation

The principle that the enthalpy change of an overall process equals the sum of the enthalpy changes of its individual steps.

Formation Reaction

A reaction in which a compound is formed from its constituent elements in their standard states.

Enthalpy of Formation ($\Delta H_f$)

The enthalpy change associated with a formation reaction.

Standard Conditions

Thermodynamic conditions where gases are at $1\,atm$ pressure, aqueous species are $1\,M$, and substances are in their standard states.

Standard State

The most stable form of a substance at $1\,atm$ pressure and the specified temperature.

Standard Enthalpy of Formation ($\Delta H^{\circ}_f$)

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

Standard Heat of Reaction ($\Delta H^{\circ}$)

The enthalpy change for a reaction calculated from standard heats of formation using $\Delta H^{\circ} = \sum \Delta H_f^{\circ}(\text{products}) - \sum \Delta H_f^{\circ}(\text{reactants})$.