lec2 - Announcements Lab started Monday Discussion has also...

1
Announcements
• Lab started Monday !!!
• Discussion has also already started !!!
• CR0 section see head TA Slava after class
• drop + re–add = disaster
• Head TA office hours: W 11–12 Chem 161
Last Time
• First Law of Thermodynamics
Δ U = q + w
– heat emitted
q → heat
+ heat absorbed
– work delivered
w → work
+ work accepted
• Know q and w → calculate Δ U
Heat → q
• Unit of heat: calorie
– 1 cal = amount of energy required to heat
1 g of H
2
O by 1 ° C
• Standard S.I. Unit: Joule
– 1 cal = 4.184 J
• Different materials heat differently

2
Basis for Comparison
• Heat capacity = heat supplied / temp. rise
c
p
=
• Officially: heat required to raise T by 1 ° C
• Units: J / ° C or J / K
• Poor measure: Extensive property
q
Δ T
Better Estimates
• Molar heat Capacity: C
p
C
p
=
• Specific heat Capacity: C
sp
C
sp
=
• Both C
p
and C
sp
are intensive properties
q
n Δ T
q
m Δ T
J
mol
°
C
J
g
°
C
Uses of C
p
and C
sp
• C
p
and C
sp
are tabulated
– calculate heat
q = nC
p
Δ T = mC
sp
Δ