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28 Cards in this Set
- Front
- Back
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thermodynamics |
study of energy and its transformations |
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thermochemistry |
branch of thermodynamics that deals with heat in chemical and physical change |
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system |
part of the universe we are focusing on |
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surroundings |
everything else around the system |
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internal energy (E) |
the sum of all energies of the system |
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ΔE |
ΔE = Efinal - Einitial = Eproducts - Ereactants ΔE = q+w the sign of energy change indicates energy flow (from the systems perspective)
(change in energy of the system = an equal and opposite change in the energy of the surroundings)
transfer of energy from system to surrounding (or vice versa) |
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two forms of energy transfer |
heat and work |
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work (w) |
the energy transferred when an object is moved by a force
+ means work is done ON the system (compression) - means work is done BY the system (expansion) |
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heat (q) |
energy transferred as a result of a difference in temperature between the system and the surroundings
+ means system gains heat - means system releases heat |
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two most important types of chemical work |
electric work: work done by moving charged particles. pressure-volume work (PV work): mechanical work done when the volume of the system changes in presence of an external pressure (P) |
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pressure-volume work |
w=-PΔV |
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enthalpy (H) |
-the thermodynamic variable that relates directly to energy changes at constant pressure -eliminates the need to measure PV work -internal energy plus the product of pressure and volume H=E+PV |
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change in enthalpy (ΔH) |
change in internal energy plus the product of pressure (which is constant) and change in volume
ΔH=ΔE+PΔV |
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wall |
separates system and surroundings adiabatic wall - perfect insulator diathermal wall - perfect conductor of heat |
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open system |
mass transfers between system and surroundings |
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closed system |
system as constant mass |
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first law of thermodynamics |
also known as law of conservation of energy = the total energy of the universe is constant
ΔEuniverse = ΔEsystem + ΔEsurroundings |
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Joule (J) |
SI unit of energy 1J = 1kgxm^2/s^2
(1 British Thermal Unit (BTU) = 1055 J) |
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calorie (cal) |
older unit defined as the quantity of energy needed to raise the temperature of 1 g of water b one degree celcius.
1 cal = 4.184 J 1J = .2390 cal |
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state function |
-the internal energy of a system -a property dependent only on the current state of the system, not on the path it took to get there
i.e.: ΔE, ΔP, ΔT, ΔV |
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heat capacity |
the quantity of heat required to change its temperature by 1K
q/ΔT = constant |
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specific heat capacity (c) |
the quantity of heat required to change the temperature of 1 grams of a substance by 1 K
c = q/massxΔT q=cmΔT |
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molar heat capacity (C) |
the quantity of heat required to change the temperature of 1 mole of a substance by 1 K
C=q/molxΔT |
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calorimeter |
device used to measure the heat released (or absorbed) by a physical or chemical process |
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thermochemical equation |
balanced equation that includes the enthalpy change of the reaction |
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Hess's Law |
the enthalpy change of an overall process is the sum of the enthalpy changes of its individual steps |
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standard states |
set of specific conditions for Hess's Law gas: 1 atm aqueous solution: 1M concentration pure substance: 1 atm and 25 decrees celcius |
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standard enthalpy of reaction ΔH⊖ |
when the enthalpy change of a reaction is measured at the standard state
(aka standard heat of reaction) |
