Represented by q. The quantity of energy that transfers from one object to another because of a temperature difference between them.
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Heat always flows from \____ to \____
A warmer object to the cooler object (it is NEVER flowing from cold to hot)
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Thermochemistry
the study of energy changes that occur during chemical reactions and changes in state
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Chemical potential energy
Energy stored in chemical bonds
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endothermic process
the system gains heat as the surroundings cool down
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Exothermic process
the system loses heat as the surroundings heat up
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Law of Conservation of Energy
In any chemical or physical process, energy is neither created nor destroyed.
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Calorie
Amount of energy needed to raise temperature 1 gram of water 1 degree C
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Joule
SI unit of energy
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heat capacity
the number of heat units needed to raise the temperature of a body by one degree. (q)
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specific heat
The amount of energy required to raise the temperature of 1 gram of a substance by 1 degree celcius
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specific heat equation
c \= q/mΔT
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Calorimetry
The precise measurement of heat flow out of a system for chemical and physical processes
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The heat released by the system is equal to
heat absorbed by surroundings
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calorimetry equation
qsystem \= -qsurroundings \= ΔH \= -m x C x ΔT
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Calorimeter
an insulated device used to measure the absorption or release of heat in chemical or physical processes
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Enthalpy
The heat content of a system at constant pressure
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thermochemical equation
a chemical equation that includes the amount of heat produced or absorbed during the reaction (enthalpy change)
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How does the quantity of heat absorbed by a melting solid compare to the quantity of heat released when the liquid solidifies?
the quantity of heat absorbed by a melting solid is exactly the same as the quantity of heat released when the liquid solidifies
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molar heat of fusion (ΔHfus)
The heat absorbed by one mole of solid substance as it melts to a liquid at a constant temperature
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molar heat of solidification (ΔHsolid)
The heat lost when one mole of a liquid solidifies at a constant temperature
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Heats of Fusion and Solidification equation
q \= mLfus (latent heat of fusion, a constant)
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How does the quantity of heat absorbed by a vaporizing liquid compare to the quantity of heat released when the vapor condenses?
the quantity of heat absorbed by a vaporizing liquid is exactly the same as the quantity of heat released when the vapor condenses
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molar heat of vaporization (ΔHvap)
The amount of heat necessary to vaporize one mole of a given liquid
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molar heat of condensation (ΔHcond)
The amount of heat released when one mol of vapor condenses at the normal boiling point
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Heats of Vaporization and Condensation Equation
q \= mLvap (latent heat of vaporization)
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During the formation of a solution, heat is
Either released or absorbed.
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molar heat of solution (ΔHsoln)
The enthalpy change caused by dissolution of one mole of substance
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Hess's law of heat summation
if you add two or more thermochemical equations to give a final equation, then you also add the heats of reaction to give the final heat of reaction
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standard heat of formation (ΔH°f)
The change in enthalpy that accompanies the formation of one mole of a compound from its elements with all substances in their standard states at 25 degrees Celsius.
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