Thermochemistry - study of heat from a chemical
os ran w/ surroundings
system - whatever is being studied- can be big or small surroundings- everything that is not part of the system open system - is able to transfer energy & mass o closed system can only transfer energy isolated system - nothing is transferred
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energy = kinetic &
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capacity to do work (W)
thermal energy - type of kinetic energy, associated
w/ movement of particles relating
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heat (q)- energy associated w/ a difference in
temperature, transferred via collisions *always transferred from hot to cold
qdo T m qamass
Csp - specific heat capacity - amount of energy
temp of required to raise? Ig of of a substance by loc
G g = MCAT SI unit for heat= calorie
food a I calorie - 4.185 calorie Ical = 1000 cal = 1 kcal
study Don't forget about the age old question of How do covalent bond and hydrogen differ?
9 = CSAT has no mass dependency Shay
(heat capacity not specific heat capacity)
chemical energy - associated w/ bonds & movement
qrxn - heat associated w/ a chemical ran occuring We also discuss several other topics like Is childhood disintegrative disorder autism?
@ a constant tennp (isotherm)
qron means reactants & products at the same temp
are Don't forget about the age old question of What protists are heterotrophic?
endothermic ron products at tq to Soup
& in general metals have low heat capacities
- if something heats up easily it has a low Don't forget about the age old question of Why is psychology more than just common sense?
specific heat capacity and visa versa
& liquid water has a high specific heat capacity
because of hydrogen bonding (even though it is small)
Ex: Calculate the heat needed to raise sog of
CG HG (benzene) from 25.
30 to 37.2°C. Csp (CC HQ) = 4.053/g°c
& AT IS the same in °C ork
q = mC sp OT = (50 g) (4.053/g°c) (37.2-25.3°c)
of Energy - energy must be conserved
qrxn = -q surroundings (9 system)
qoxn + q sur = 0
*if one thing loses heat, something else will gain it
Bomb calorimeter - apparatus that allows for study
of heat exchange
• can calculate heat capacities te
• must have excess oxygen inside for complete
combustion of the sample
•change in temp of the water is used to determine
the specific heat capacity
q combustion (com) - heat evolved in a combusion ran
Problem of the day
q= (2379) (4.18 3/9°c)(37-23°c) = 13,869.243) 13,869 5/Ical II Cal -
3.318 Cal 14.185 11000 cal
1/8/16 Lecture 3
W/ change in tempe use q=mcoT
If z>T,, ball loses heat & - Calorimeter gains heat'
& cal = q cups + 2Hot ... = Ceal + q Hzo
une in cludes everything moon an n o part of calorimeter *cannot have a phase change qrxn = diff in energy between reactants/products
@ same tempo
•work - force
acting over a distance = pressure volume work,
Ifi angas > 0, expansion
on gasco, compression
OV for expansion => positive
• work is done by the system
(* 1 l-atm = 101.33)
W3o =) work is done on the
Ex: calculate the quantity of work
3.5L expansion of a gas against
pressure of 748mm Hg. Love
associated w/ a an external
W = -Pext AV => (-748 mm Hg)/latm
1760 mmHg = -3.4 L'atm
-3.4 Lam 101.3.5 = (-3.5 x 10250
EX: A sample gives off 5228 cal when bumed in
a calorimeter, The AT of calorimeter is 4.39°C. What is the heat capacity of the calorimeter?
q sample = -qeal tqtzo if H2o is given -5228 cal = -Cear OT = - Ccal (4.39°c)
Ceal = 5228 cal = 11190.89 cal foc
4.39 °C 1190.89 cal 4.185
important & 1st law of thermodynamics.
AU = qtw
w/ capital =) state function - trait only depends on initial
& final states of system a w/ lower case => path function - overall value depends on.
path it takes - distance traveled (path function)
altitude (state function)
constant volume: Ov=0
su =q+w a w=-por
ou = qtw pole = q-par
=> AU + PAV = qe
AH = enthalpy