Heating - PowerPoint PPT Presentation

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Heating

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Freezing (solidification) sublimation deposition All Phase changes accompanied by energy changes Phase changes are physical changes: sometimes energy is absorbed ... – PowerPoint PPT presentation

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Title: Heating


1
Heating Cooling CurvesDo Now Name the phase
changeS ? LL ? GG ? LL ? SS ? GG ? S
Melting (fusion)
Boiling (vaporization)
condensation
Freezing (solidification)
sublimation
deposition
2
All Phase changes accompanied by energy changes
  • Phase changes are physical changes
  • sometimes energy is absorbed (endothermic)
  • sometimes energy is released (exothermic)
  • Energy change for given phase change can be
    measured/calculated (were going to learn how to
    do this tomorrow)

3
  • As you go from S ? L ? G, you are increasing the
    distance between molecules, so you are increasing
    their PE !
  • We can see these energy changes by looking at a
    heat/cooling curve next slide

Endothermic
Sublimation Vaporization Melting (fusion)
Deposition Condensation Freezing
(solidification)
Gas
PE
Liquid
Solid
Exothermic
4
TURN TO PACKET page 11, take notes here
5
III
IV
V
Liquid Gas
Gas
Solid Liquid
Liquid
Solid
?
Boil pt.
Temperature
Melt pt.
?
K.E.?
K.E.?
K.E.?
K.E.?
P.E.?
P.E.?
P.E.?
P.E.?
P.E.?
Time
6
During Phase changes
  • More than one phase is present
  • Melting solid and liquid
  • Boiling liquid and gas
  • (lets check out a tiger animation)
  • temperature is constant ?T0
  • There is no change in temp!!!!!
  • NOTE if 2 phases are present, temp is
    constant

7
Melting Boiling Points
  • Plateaus Phase changes PE changes
  • always given as temp (C, K)
  • WHY IS IT CALLED A POINT?

8
QUICK QUESTIONWhat happens to temperature as
heat is added at boiling point?
  • Nothing, temp doesn'tt change until only 1 phase
    is present!

9
What do you think a cooling curve would look like?
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