Flashcards in Thermodynamics Deck (29)
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1
thermochemistry
study of energy changes that occur during chemical reactions and changes in state
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Two types of energy
Chemical Potential Energy (PE)
Kinetic Energy (KE)
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chemical potential energy
energy stored within a chemical bond
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kinetic energy
energy of motion
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2 Laws of Thermodynamics
1. law of conservation of energy
2. High energy to low energy; high temperature to low temperature
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Heat
Form of energy that flows
Always travels from warm areas to cool areas
high kinetic energy areas to low kinetic eergy areas
7
temperature
a measure of average kinetic energy of particles. As the average kinetic energy of the particles increases, the temperature increases
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Units for heat
Joules (J) Kilojoules (kJ)
calorie (cal) Kilocalories (C)
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calorie to joule conversion
1 cal = 4.184 J
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joule to kilojoule
calorie to kilocalorie
conversions
1000 joules = 1 kilojoule
1000 calories = 1 kilocalorie
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On a heating/cooling curve, the flat surfaces show...
potential energy
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On a heating/cooling curve, the upward sloping lines show...
kinetic energy
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Heat capacity
the amount of heat needed to raise the temperature of something 1 degree celcius
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Heat capacity depends on...
1. how much substance you have (mass)
2. the chemical composition
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specific heat capacity equation and meaning of variables
q = m*c*delta(T)
q = heat (J)
m = mass (g)
delta(T) = change in temp.
Cp = specific heat capacity
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Exothermic reaction
the system releases heat to the surroundings
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Endothermic reaction
the system absorbs heat from the surroundings
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calorimetry
precise measurement of heat flow in or out of the system during a chemical or physical process
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Equation for heat of fusion/vaporization and meaning of variables
q = delta(H) * mol
q = heat
mol = moles
delta(H) = enthalpy
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enthalpy
heat content of a system
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Heat of fusion (melting)
heat/mole asorbed to melt a substance
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Heat of vaporization
heat/mol needed to vaporize a substance
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Thermochemical equation
contains the enthalpy (hea) change when a chemical reaction takes place
can be written two ways
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In an endothermic reaction, the enthalpy symbol...
is included on the reactant side
written with a plus
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In an exothermic reaction, the enthalpy symbol...
is included on the product side
written with a negative
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All decomposition reactants are...
endothermic
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3 Exothermic phase changes
1. condensation
2. freezing
3. deposition
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3 endothermic phase changes
1. evaporation
2. melting
3. sublimation
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