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Chemistry: Atoms First

Key Terms

Chemistry: Atoms FirstKey Terms

bomb calorimeter
device designed to measure the energy change for processes occurring under conditions of constant volume; commonly used for reactions involving solid and gaseous reactants or products
bond energy
(also, bond dissociation energy) energy required to break a covalent bond in a gaseous substance
Born-Haber cycle
thermochemical cycle relating the various energetic steps involved in the formation of an ionic solid from the relevant elements
calorie (cal)
unit of heat or other energy; the amount of energy required to raise 1 gram of water by 1 degree Celsius; 1 cal is defined as 4.184 J
device used to measure the amount of heat absorbed or released in a chemical or physical process
process of measuring the amount of heat involved in a chemical or physical process
chemical thermodynamics
area of science that deals with the relationships between heat, work, and all forms of energy associated with chemical and physical processes
endothermic process
chemical reaction or physical change that absorbs heat
capacity to supply heat or do work
enthalpy (H)
sum of a system’s internal energy and the mathematical product of its pressure and volume
enthalpy change (ΔH)
heat released or absorbed by a system under constant pressure during a chemical or physical process
exothermic process
chemical reaction or physical change that releases heat
expansion work (pressure-volume work)
work done as a system expands or contracts against external pressure
first law of thermodynamics
internal energy of a system changes due to heat flow in or out of the system or work done on or by the system
heat (q)
transfer of thermal energy between two bodies
heat capacity (C)
extensive property of a body of matter that represents the quantity of heat required to increase its temperature by 1 degree Celsius (or 1 kelvin)
Hess’s law
if a process can be represented as the sum of several steps, the enthalpy change of the process equals the sum of the enthalpy changes of the steps
compound composed only of hydrogen and carbon; the major component of fossil fuels
internal energy (U)
total of all possible kinds of energy present in a substance or substances
joule (J)
SI unit of energy; 1 joule is the kinetic energy of an object with a mass of 2 kilograms moving with a velocity of 1 meter per second, 1 J = 1 kg m2/s and 4.184 J = 1 cal
kinetic energy
energy of a moving body, in joules, equal to 12mv212mv2 (where m = mass and v = velocity)
lattice energy (ΔHlattice)
energy required to separate one mole of an ionic solid into its component gaseous ions
nutritional calorie (Calorie)
unit used for quantifying energy provided by digestion of foods, defined as 1000 cal or 1 kcal
potential energy
energy of a particle or system of particles derived from relative position, composition, or condition
specific heat capacity (c)
intensive property of a substance that represents the quantity of heat required to raise the temperature of 1 gram of the substance by 1 degree Celsius (or 1 kelvin)
standard enthalpy of combustion (ΔHc°)(ΔHc°)
heat released when one mole of a compound undergoes complete combustion under standard conditions
standard enthalpy of formation (ΔHf°)(ΔHf°)
enthalpy change of a chemical reaction in which 1 mole of a pure substance is formed from its elements in their most stable states under standard state conditions
standard state
set of physical conditions as accepted as common reference conditions for reporting thermodynamic properties; 1 bar of pressure, and solutions at 1 molar concentrations, usually at a temperature of 298.15 K
state function
property depending only on the state of a system, and not the path taken to reach that state
all matter other than the system being studied
portion of matter undergoing a chemical or physical change being studied
intensive property of matter that is a quantitative measure of “hotness” and “coldness”
thermal energy
kinetic energy associated with the random motion of atoms and molecules
study of measuring the amount of heat absorbed or released during a chemical reaction or a physical change
work (w)
energy transfer due to changes in external, macroscopic variables such as pressure and volume; or causing matter to move against an opposing force
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