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38 Cards in this Set
- Front
- Back
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Energy
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the capacity to do work or produce heat
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Law of conservation of energy
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states that in any chemical reaction or physical process, energy may change from one form to another, but it is neither created nor destroyed.
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Chemical potential energy
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the energy stored in a substance because of its composition
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heat
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a form of energy that flows from a warmer object to a cooler object
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calorie
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the amount of heat required to raise the temperature of one gram of pure water by one degree Celsius
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joule
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the SI unit of heat and energy
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specific heat
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The amount of heat required to raise the temperature of one gram of a given substance by one degree Celsius.
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calorimeter
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An insulated device that is used to measure the amount of heat released or absorbed during a physical or chemical process.
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thermochemistry
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: the study of heat changes that accompany chemical reactions and phase changes.
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system
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the specific part of the universe containing the reaction or process being studied.
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surroundings
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includes everything in the universe except the system.
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universe
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the system plus surroundings.
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enthalpy
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: the heat content of a system at constant pressure.
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enthalpy (heat) of reaction
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the change in enthalpy for a reaction—the difference between the enthalpy of the substances that exist at the end of the reaction and the enthalpy of the substances present at the start
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thermochemical equation
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a balanced chemical equation that includes the physical states of all the reactants and the energy change, usually expressed as the change in enthalpy.
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Enthalpy (heat) of combustion
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The enthalpy change for the complete burning of one mole of a given substance.
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molar enthalpy (heat) of vaporization
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the amount of heat required to vaporize one mole of a liquid
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Molar enthalpy (heat) of fusion
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the amount of heat required to melt one mole of a solid substance.
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allotrope
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one of two or more forms of an element with different structures and properties when they are in the same state—solid, liquid, gas.
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Hess's law
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States that if two or more thermochemical equations can be added 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 final reaction.
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standard enthalpy (head) of formation
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the change in enthalpy that accompanies the formation of one mole of a compound in its standard state from its constituent elements in their standard states.
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VAPORIZATION
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the energy-requiring process by which a liquid changes to a gas or vapor
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entropy
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A measure of the number of possible ways that the energy of a system can be distributed
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free energy
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the energy available to do work—the difference between the change in enthalpy and the product of the entropy change and the Kelvin temperature.
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Thermodynamic standard condition
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278 K, 100 kpa
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the total amount of energy in the eniverse is constant ( law of conservation of energy)
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First law of thermodynamics
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spontaneous changes in the universe tend toward a state of greater disorder
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Second law of thermodynamics
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the entropy of a pure, perfect, crystalline substance is infinitely ordered and at absolute zero is 0
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Third law of thermodynamics
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U = q + w
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internal energy = heat given off or absorbed + work done by the system
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state functions
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property that depends on only the surrent state of a system, not the path the system took to get there
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H<0
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endothermic
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H>0
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exothermic
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S>0
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high disorder
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S<0
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low disorder
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G<0
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Spontaneous
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G>0
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nonspontaneous
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isobaric
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pressure stays constant
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isothermal
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temperature stays constant
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