Chapter 6: Energy and Thermochemistry

Vocabulary flashcards covering fundamental thermodynamics, thermochemistry concepts, energy units, heat capacity, enthalpy, calorimetry, and Hess's law from Chapter 6.

Thermodynamics

The study of the relationship between energy and temperature changes.

Thermochemistry

The branch of thermodynamics that deals specifically with chemical changes.

Potential Energy

Stored energy, or energy that results from position in a field of force.

Kinetic Energy

The energy of motion.

System

The specific chemical reaction or process being studied.

Surroundings

Everything around the system.

Exothermic Reaction

A process or reaction in which the system releases heat to the surroundings ($q < 0$).

Endothermic Reaction

A process or reaction in which the system absorbs heat from the surroundings ($q > 0$).

First Law of Thermodynamics

The law of conservation of energy stating that energy can neither be created nor destroyed; energy lost by the system is gained by the surroundings, and energy gained by the system is lost by the surroundings.

Pressure-Volume Work

Work done when a gas expands or contracts against external pressure, calculated by the equation $w = -P\times \text{d}V$.

Enthalpy ($H$)

A measure of the total heat content of a system.

Change in Enthalpy ($\Delta H$)

The gain or loss of heat energy as the result of a chemical or physical change at constant pressure.

Specific Heat Capacity ($s$)

The amount of heat required to increase the temperature of one gram of a substance by $1\,^{\circ}\text{C}$, expressed as $s = \frac{q}{m\times \Delta T}$.

Heat Capacity ($C$)

The amount of heat required to raise the temperature of an object regardless of the object's mass, expressed as $C = \frac{q}{\Delta T}$.

Calorimetry

The experimental measurement of heat flow, conducted either at constant pressure or constant volume.

Coffee Cup Calorimetry

A laboratory method used for constant pressure calorimetry to monitor heat changes in solution.

Constant Volume Calorimetry (Bomb Calorimetry)

A technique used to measure heats of reaction for fuels and high-energy chemical reactions using a rigid container constructed to prohibit expansion so volume remains constant.

Extensive Property

A physical or chemical property (such as the heat released or absorbed in a reaction) that depends directly upon the amount of matter present.

Reaction Enthalpy ($\Delta H^{\circ}_{\text{rxn}}$)

The heat transfer that accompanies a chemical reaction at constant pressure.

State Function

A property that depends only on the current state of the system and is completely independent of the path or process by which the system reached that state.

Hess's Law

The principle stating that if a reaction occurs in several steps, the overall enthalpy change is equal to the sum of the enthalpy changes for the individual steps.

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

The enthalpy change when one mole of any substance forms from its constituent elements in their standard states under standard conditions ($1\,\text{bar} = 0.9869\,\text{atm}$ and typically $298.15\,\text{K}$).