Chapter 16 - Energy and Chemical Change Vocabulary

heat

A form of energy that flows from a warmer object to a cooler object.

joule

The SI unit of heat and energy.

molar enthalpy (heat) of vaporization

The amount of heat required to evaporate one mole of a liquid.

thermochemical equation

A balanced chemical equation that includes the physical states of all the reactants and products and specifies the change in enthalpy.

entropy

A measure of the disorder or randomness of the particles of a solution.

spontaneous process

A physical or chemical change that occurs without outside intervention and may require energy to be supplied to begin the process.

calorimeter

An insulated device that is used to measure the amount of heat released or absorbed during a physical or chemical process.

surroundings

In thermochemistry, includes everything in the universe except the system.

universe

In thermochemistry, is the system plus the surroundings.

system

In thermochemistry, the specific part of the universe containing the reaction or process being studied.

Hess's Law

States that if two or more thermochemical equations can be added to produce a final equation for a reaction, the sum of the enthalpy changes for the individual reactions is the enthalpy change for the final reaction.

law of conservation of energy

States that in any chemical or physical process, energy may change from one form to another but is neither created nor destroyed.

law of disorder

States that the entropy of the universe must increase as a result of a spontaneous reaction or process.

molar enthalpy (heat) of fusion

The amount of heat required to melt one mole of a solid substance.

specific heat

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

calorie

The amount of heat required to raise the temperature of one gram of pure water by one degree Celsius.

energy

The capacity to do work or produce heat; exists as potential energy, which is stored in an object due to its composition or position, and kinetic energy, which is the energy of motion.

enthalpy (heat) of reaction

The change in enthalpy for a reaction - the difference between the enthalpy of the substances that exist at the end of the reaction and the enthalpy of the substances present at the start.

standard enthalpy (heat) of formation

The change in enthalpy that accompanies the formation of one mole of a compound in its standard state from its constituent elements in their standard states.

chemical potential energy

The energy stored in a substance because of its composition; is released or absorbed as heat during chemical reactions or processes.

free energy

The energy that is available to do work - the difference between the change in enthalpy and the product of the entropy change and the absolute temperature.

enthalpy (heat) of combustion

The enthalpy change for the complete burning of one mole of a given substance.

enthalpy

The heat content of a system at constant pressure.

thermochemistry

The study of heat changes that accompany chemical reactions and phase changes.