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Chemistry LibreTexts

5.4: Key Terms

  • Page ID
    415169
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    Example and Directions
    Words (or words that have the same definition)The definition is case sensitive(Optional) Image to display with the definition [Not displayed in Glossary, only in pop-up on pages](Optional) Caption for Image(Optional) External or Internal Link(Optional) Source for Definition
    (Eg. "Genetic, Hereditary, DNA ...")(Eg. "Relating to genes or heredity")The infamous double helix https://bio.libretexts.org/CC-BY-SA; Delmar Larsen
    Glossary Entries
    Word(s)DefinitionImageCaptionLinkSource
    bomb calorimeterdevice 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    
    calorimeterdevice used to measure the amount of heat absorbed or released in a chemical or physical process    
    calorimetryprocess of measuring the amount of heat involved in a chemical or physical process    
    chemical thermodynamicsarea of science that deals with the relationships between heat, work, and all forms of energy associated with chemical and physical processes    
    endothermic processchemical reaction or physical change that absorbs heat    
    energycapacity 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 processchemical 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 thermodynamicsinternal 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 lawif 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    
    hydrocarboncompound 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 energyenergy 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 energyenergy 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 stateset 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 functionproperty depending only on the state of a system, and not the path taken to reach that state    
    surroundingsall matter other than the system being studied    
    systemportion of matter undergoing a chemical or physical change being studied    
    temperatureintensive property of matter that is a quantitative measure of “hotness” and “coldness”    
    thermal energykinetic energy associated with the random motion of atoms and molecules    
    thermochemistrystudy 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    

    5.4: Key Terms is shared under a CC BY 4.0 license and was authored, remixed, and/or curated by LibreTexts.

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