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bomb calorimeter
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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
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calorie (cal)
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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
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calorimeter
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device used to measure the amount of heat absorbed or released in a chemical or physical process
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calorimetry
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process of measuring the amount of heat involved in a chemical or physical process
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chemical thermodynamics
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area of science that deals with the relationships between heat, work, and all forms of energy associated with chemical and physical processes
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endothermic process
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chemical reaction or physical change that absorbs heat
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energy
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capacity to supply heat or do work
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enthalpy (
H
)
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sum of a system’s internal energy and the mathematical product of its pressure and volume
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enthalpy change (Δ
H
)
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heat released or absorbed by a system under constant pressure during a chemical or physical process
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exothermic process
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chemical reaction or physical change that releases heat
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expansion work (pressure-volume work)
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work done as a system expands or contracts against external pressure
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first law of thermodynamics
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internal energy of a system changes due to heat flow in or out of the system or work done on or by the system
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heat (
q
)
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transfer of thermal energy between two bodies
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heat capacity (
C
)
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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)
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Hess’s law
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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
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hydrocarbon
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compound composed only of hydrogen and carbon; the major component of fossil fuels
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internal energy (
U
)
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total of all possible kinds of energy present in a substance or substances
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joule (J)
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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 m
2
/s and 4.184 J = 1 cal
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kinetic energy
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energy of a moving body, in joules, equal to (where
m
= mass and
v
= velocity)
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nutritional calorie (Calorie)
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unit used for quantifying energy provided by digestion of foods, defined as 1000 cal or 1 kcal
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potential energy
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energy of a particle or system of particles derived from relative position, composition, or condition
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specific heat capacity (
c
)
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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)
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standard enthalpy of combustion
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heat released when one mole of a compound undergoes complete combustion under standard conditions
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standard enthalpy of formation
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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
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standard state
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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
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state function
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property depending only on the state of a system, and not the path taken to reach that state
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surroundings
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all matter other than the system being studied
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system
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portion of matter undergoing a chemical or physical change being studied
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temperature
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intensive property of matter that is a quantitative measure of “hotness” and “coldness”
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thermal energy
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kinetic energy associated with the random motion of atoms and molecules
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thermochemistry
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study of measuring the amount of heat absorbed or released during a chemical reaction or a physical change
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work (
w
)
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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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