5.4: Key Terms
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- Aug 26, 2023
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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
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
calorimeter | device used to measure the amount of heat absorbed or released in a chemical or physical process
calorimetry | 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
energy | 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
hydrocarbon | 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 (where m = mass and v = velocity)
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 | heat released when one mole of a compound undergoes complete combustion under standard conditions
standard enthalpy of formation | 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
surroundings | all matter other than the system being studied
system | portion of matter undergoing a chemical or physical change being studied
temperature | 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
thermochemistry | 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
