Studied by 0 peopleheat
Represented by q. The quantity of energy that transfers from one object to another because of a temperature difference between them.
Heat always flows from ____ to ____
A warmer object to the cooler object (it is NEVER flowing from cold to hot)
Thermochemistry
the study of energy changes that occur during chemical reactions and changes in state
Chemical potential energy
Energy stored in chemical bonds
endothermic process
the system gains heat as the surroundings cool down
Exothermic process
the system loses heat as the surroundings heat up
Law of Conservation of Energy
In any chemical or physical process, energy is neither created nor destroyed.
Calorie
Amount of energy needed to raise temperature 1 gram of water 1 degree C
Joule
SI unit of energy
heat capacity
the number of heat units needed to raise the temperature of a body by one degree. (q)
specific heat
The amount of energy required to raise the temperature of 1 gram of a substance by 1 degree celcius
specific heat equation
c = q/mΔT
Calorimetry
The precise measurement of heat flow out of a system for chemical and physical processes
The heat released by the system is equal to
heat absorbed by surroundings
calorimetry equation
qsystem = -qsurroundings = ΔH = -m x C x ΔT
Calorimeter
an insulated device used to measure the absorption or release of heat in chemical or physical processes
Enthalpy
The heat content of a system at constant pressure
thermochemical equation
a chemical equation that includes the amount of heat produced or absorbed during the reaction (enthalpy change)
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
molar heat of fusion (ΔHfus)
The heat absorbed by one mole of solid substance as it melts to a liquid at a constant temperature
molar heat of solidification (ΔHsolid)
The heat lost when one mole of a liquid solidifies at a constant temperature
Heats of Fusion and Solidification equation
q = mLfus (latent heat of fusion, a constant)
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
molar heat of vaporization (ΔHvap)
The amount of heat necessary to vaporize one mole of a given liquid
molar heat of condensation (ΔHcond)
The amount of heat released when one mol of vapor condenses at the normal boiling point
Heats of Vaporization and Condensation Equation
q = mLvap (latent heat of vaporization)
During the formation of a solution, heat is
Either released or absorbed.
molar heat of solution (ΔHsoln)
The enthalpy change caused by dissolution of one mole of substance
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
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.
Note
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