Chemistry Lect 3
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- Extensive: change with the amount (i.e. V, n)
- Intensive: don't (i.e. P and Temp)
Types of Heat Transfer
- Radiation (the only type of heat trans that travels through a vacuum)
In which direction does heat travel?
- From hot to cold
- * remember that any energy transfer that is not heat is work!
What kind of function is work?
A pathway function - different pathways = different amounts of work
Can a system at rest do work?
A system at rest can still do PV work (must have a change in volume)
First Law of Thermodynamics
- ΔE = q + W
- the change in energy is = to the heat flow into plus the work done on the system
Second Law of Thermodynamics
heat cannot be completely converted to work in a cyclical process
Temp is related to:
- how fast molecules are moving/vibrating
- KEave = 3/2 KT
- K: 1.38*10-23 J/K
Pressure is what kind of property?
- Intensive (does not change with amount)
- the greater the KE/V the greater the pressure
- ΔH = U + PV
- if no change in volume than PV=0 and ΔH=U
- ΔHRxn = ΔHProds - ΔHReactants
- if ΔH is neg then the rxn is exothermic (releases heat)
- tendency towards disorder
- the more likely a situation is the more entropy it will have
- on the MCAT a rxn must increase ΔSUniverse in order to proceed
- rxns at equilibrium have reached max SUniverse
Gibbs Free Energy
- ΔG = ΔH - TΔS
- an extensive property (changes with amount)
- a neg G indicates an increase in ΔSUniverse and therefore is spontaneous
- (-)ΔG and (-)ΔH = (+)ΔS --> spontaneous for sure
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