Grade 12 Chemistry: Thermochemistry and Reaction Rates
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Course
Chemistry
Institution
12th Grade
Grade 12 Chemistry Notes on Thermochemistry and Reaction Rates. The document includes topics ranging from energy transformations, changes in enthalpy, law of thermodynamics, law of conservation of energy, writing thermochemical equations, calorimetry, hess's law, standard molar enthalpy of formatio...
UNIT2 THERMOCHEMISTRY AND REACTION
RATES
wecalculatechangein energy nottotalenergy
totalenergyinvolvespotentialenergyto breakbondsand so forthwhichis why wedon't calculatefortotal energy
law of conservation of Energy Energy cannot becreated or destroyed
in an open systemheatandmattercan leave
in a closedsystemheatenergy leaves not matter
in an isolatedsystemnothingleaves
A system is thepartofthe universe that youare observingstudying
Thesystemis thespecificpartof the is ofinterest tostudy
surroundings Allotherparts of the gigggethat
study notunderinvestigation therestoftheuniverse
OPEN closed ISOLATED
Matter
I mapour
Heat treat
massandenergy energy nothing
leaves leaves leaves
changeon canexchangeneither
andenergywiththe energywith
thesurround energy normatterwith
surroundings eg open ingssmatterremainsfixed its surroundinge.g
reactionAlas route flask thermosflask
eg asealedreaction
system surrounding
open closed isolated
mm
surrounding
a mains
is
Ys Teaches system
caches s ca p acicag
soluteesait meat
of waterbeforeandaftersalt canindicate energy transferchange
temperature
Assumewateris onlysurrounding majorityof heatabsorbedbywaterothersurroundings negligible
Example
H2ois i those
neat
ice
IN
hand
colddoesn'texistonlyabsence ofheat
,QWhatare examples of energy transformations
Gasoline in car
Cellularrespiration
cooking Food
THERMOCHEMISTRY
THE PROCESS OF HEAT TRANSFORMATION IS CALLED
or
changes in heat duringa reaction
3 Types of REACTIONS
chemical Governed by 1stlawof thermodynamics
Physical Energy cannot be created or destroyed
todo
capacity work
typesof energy
1 Chemical theenergy storedwithinthebondsof chemical substances
2 Nuclear theenergystoredwithinthe collectionofneutronsand protons in the atom
3Thermal the total ke and Pe of atoms andmolecules in a substance
a Electrical the energyassociated withthe flow of electrons
5kinetic Energy inmotion
6Potential Energyavailablebyvirtueof an object's position
unitsforenergyJoulesis
root 1kt
Heatand work energyintransit alsomeasuredinjoules
caloriecoal
ican a isat
1 calorieis the energy needed to raise the temperature of Ig ofwater by soc
ENERGYCHANGES IN CHEMICALREACTIONS
Heatis the transfer ofthermalenergy betweentwo bodies thatare at differenttemperatures
temperature is a measure of kineticenergy
temperature is averageofhow fastmolecules are moving average of kineticenergy
thermalEnergy the total quantity of kineticandpotentialenergyin a substance
considers thetotalmass
thermalenergydepends on howmuch of the substance youhave
TEMPERATURE THERMAL ENERGY
0 0 s Two coffeecupsmayhavethesametemperature butjustbecausethereare 2 ofthem
soc ose ose
this doesn'tdouble the temperature However itdoesdoublethe thermalenergy
temperature osc compared to one cup of coffeebecause the masssizehasdoubled
ave ke and coffeehas a highertemperature but an iceberghasmorethermalenergy because it
thermal e doubles is not at absolute o andhasmoremassand a greatersize
, Exothermic neat leaving thesystemicontainergetsnotexothermicsystemlostenergyeventhoughcontainerisnot
out
energyneat is a product Ahan toot
It'sany process thatgivesoffheat transfers thermal energy fromsystem to the surroundings
2Hug tozig i 2those energy
Haag those tenergy
r n
e
e r s
surroundings
Endothermic neat required by thesystem
in
eatis a reactant Daren too
DH
change inneat
g
energyneat on genthalpy
it's anyprocessinwhichheathas to besuppliedto the surroundings
tangois iangle 02cg
energy
energy trois ithose
FIEF
surroundings
MELTINGBOILING
00,0 oooo 00
00000
q or 0
agio i too t.io o.io i
m bondmaking
heatenergyout
whenthe energy ofbonds that breakis lessthan theenergy whenbondsareformed the reaction is exothermic
CHEMICALENERGY
Energyrequiredto breakbonds
Energy is releasedwhennewbondsareformed
Allchemicalreactionseither
oliberateneatexothermic energyto break energytoformbond
oabsorbheat endothermic energy tobreak energytoformbonds
Enthalpyof thereaction thedifferencein energyheatbetweenreactants andproducts
thermodynamics thestudyofenergytransformationsthatoccurin a collection of matter
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