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Phase Changes Phase Diagrams and Heating Curves
13

Phase Changes Phase Diagrams and Heating Curves. Phase Diagrams Show the phases of a substance at different temps and pressures. Courtesy Christy Johannesson.

Jan 13, 2016

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Page 1: Phase Changes Phase Diagrams and Heating Curves. Phase Diagrams  Show the phases of a substance at different temps and pressures. Courtesy Christy Johannesson.

Phase ChangesPhase Changes

Phase Diagrams and Heating Curves

Page 2: Phase Changes Phase Diagrams and Heating Curves. Phase Diagrams  Show the phases of a substance at different temps and pressures. Courtesy Christy Johannesson.

Phase DiagramsPhase Diagrams

Show the phases of a substance at different temps and pressures.

Courtesy Christy Johannesson www.nisd.net/communicationsarts/pages/chem

Page 3: Phase Changes Phase Diagrams and Heating Curves. Phase Diagrams  Show the phases of a substance at different temps and pressures. Courtesy Christy Johannesson.

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

Page 4: Phase Changes Phase Diagrams and Heating Curves. Phase Diagrams  Show the phases of a substance at different temps and pressures. Courtesy Christy Johannesson.

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

Page 5: Phase Changes Phase Diagrams and Heating Curves. Phase Diagrams  Show the phases of a substance at different temps and pressures. Courtesy Christy Johannesson.

Critical PointCritical Point

Critical point: the temperature (called critical temperature) above which a substance will always be as gas regardless of the pressure

Page 6: Phase Changes Phase Diagrams and Heating Curves. Phase Diagrams  Show the phases of a substance at different temps and pressures. Courtesy Christy Johannesson.

Triple PointTriple Point

Pressure and temperature where all three phases of matter exist AT THE SAME TIME!!

http://www.youtube.com/watch?v=BLRqpJN9zeA

Page 7: Phase Changes Phase Diagrams and Heating Curves. Phase Diagrams  Show the phases of a substance at different temps and pressures. Courtesy Christy Johannesson.

Law of Conservation of Energy

Law of Conservation of Energy

Eafter = Ebefore

2 H2 + O2 2 H2O + energy

+ + WOOF!

Page 8: Phase Changes Phase Diagrams and Heating Curves. Phase Diagrams  Show the phases of a substance at different temps and pressures. Courtesy Christy Johannesson.

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!

Page 9: Phase Changes Phase Diagrams and Heating Curves. Phase Diagrams  Show the phases of a substance at different temps and pressures. Courtesy Christy Johannesson.

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

Page 10: Phase Changes Phase Diagrams and Heating Curves. Phase Diagrams  Show the phases of a substance at different temps and pressures. Courtesy Christy Johannesson.

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

Page 11: Phase Changes Phase Diagrams and Heating Curves. Phase Diagrams  Show the phases of a substance at different temps and pressures. Courtesy Christy Johannesson.

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

Page 12: Phase Changes Phase Diagrams and Heating Curves. Phase Diagrams  Show the phases of a substance at different temps and pressures. Courtesy Christy Johannesson.

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

Page 13: Phase Changes Phase Diagrams and Heating Curves. Phase Diagrams  Show the phases of a substance at different temps and pressures. Courtesy Christy Johannesson.

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