energy
the ability to do work or produce heat; exists in two basic forms (potential energy and kinetic energy)
law of conservation of energy
states that in any chemical reaction or physical process, energy can be converted from one form to another, but it is neither created nor destroyed (also known as first law of thermodynamics)
chemical potential energy
energy stored in the chemical bonds of a substance because of its composition; plays important role in chemical reactions
heat
represented by symbol q; energy that is in the process of flowing from a warmer object to a cooler object
calorie (cal)
the amount of heat required to raise the temperature of one gram of pure water by one degree Celsius
joule (J)
SI unit of heat and energy; one joule is the equivalent of 0.2390 cal, or one cal equals 4.184 joules
specific heat
the amount of heat required to raise the temperature of one gram of that substance by one degree Celsius
calorimeter
an insulated device used for measuring the amount of heat absorbed or released during a chemical or physical process
thermochemistry
the study of heat changes that accompany chemical reactions and phase changes
system
the specific part of the universe that contains the reaction or process you wish to study
surroundings
everything in the universe other that the system
universe
the system plus the surroundings; universe = system + surroundings
enthalpy (H)
the heat content of a system at constant pressure
enthalpy (heat) of reaction
the change in enthalpy for a reaction
thermochemical equation
a balanced chemical equation that includes the physical states of all reactants and products and the energy change, usually expressed as the change in enthalpy
enthalpy (heat) of combustion
the enthalpy change for the complete burning of one mole of the substance
molar enthalpy (heat) of vaporization
the heat required to vaporize one mole of a liquid
molar enthalpy (heat) of fusion
the heat required to melt one mole of a solid substance
hess's law
states that if you can add two or more thermochemical equations to produce a final equation for a reaction, then the sum of the enthalpy changes for the individual reactions is the enthalpy change for the fianl reaction
standard enthalpy (heat) of formation
the change in enthalpy that accompanies the formation of one mole of the compound in its standard state from its constituent elements in their standard states
spontaneous process
a physical or chemical change that occurs with no outside intervention
entropy (S)
a measure of the disorder or randomness of the particles that make up a system
law of disorder
states that spontaneous processes always proceed in such a way that the entropy of the universe increases
free energy
energy that is available to do work