phase changes phase diagrams and heating curves. phase diagrams show the phases of a substance at...
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Phase ChangesPhase Changes
Phase Diagrams and Heating Curves
Phase DiagramsPhase Diagrams
Show the phases of a substance at different temps and pressures.
Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
Triple Point Plot
LeMay Jr, Beall, Robblee, Brower, Chemistry Connections to Our Changing World , 1996, page 488
solidliquid
gas
melting
freezing
sublimation
deposition
vaporization
condensation
Temperature (oC)
Pre
ssur
e (a
tm)
0.6
2.6
Liquid VaporSolid
Normalmelting point
Normalboilingpoint
101.3
0.61
0.016 1000Temperature (oC)
Pre
ssu
re (
KP
a)
Triple point
Criticalpressure
Critical point
Critical temperature
373.99
22,058
Critical PointCritical Point
Critical point: the temperature (called critical temperature) above which a substance will always be as gas regardless of the pressure
Triple PointTriple Point
Pressure and temperature where all three phases of matter exist AT THE SAME TIME!!
http://www.youtube.com/watch?v=BLRqpJN9zeA
Law of Conservation of Energy
Law of Conservation of Energy
Eafter = Ebefore
2 H2 + O2 2 H2O + energy
+ + WOOF!
Law of Conservation of Energy
Law of Conservation of Energy
ENERGY
CO2 + H2OC2H2 + O2
PEreactants
PEproducts
KEstopper
heat, light, sound
Eafter = Ebefore
2 H2 + O2 2 H2O + energy
+ + WOOF!
Law of Conservation of Energy
Law of Conservation of Energy
ENERGY
C2H2 + O2C2H2 + O2
PEreactants
PEproducts
KEstopper
heat, light, sound
Eafter = Ebefore
2C2H2 + 5O2 4 CO2 + 2H2O + energy
Heating CurvesHeating CurvesT
emp
erat
ure
(oC
)
40
20
0
-20
-40
-60
-80
-100
120
100
80
60
140
Time
Melting - PE
Solid - KE
Liquid - KE
Boiling - PE
Gas - KE
Heating CurvesHeating Curves
Temperature Change• change in KE (molecular motion) • depends on heat capacity
Heat Capacity• energy required to raise the temp of 1
gram of a substance by 1°C• Water has a very high heat capacity
Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
Heating CurvesHeating Curves
Phase Change• change in PE (molecular arrangement)• temp remains constant
Heat of Fusion (Hfus)
• energy required to melt 1 gram of a substance at its m.p.
Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem
Heating CurvesHeating Curves
Heat of Vaporization (Hvap)
• energy required to boil 1 gram of a substance at its b.p.
• usually larger than Hfus…why?
EX: sweating, steam burns, the drinking bird
Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem