8/7/2019 11 Melting & Boiling
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MELTING
&BOILING
TOPIC 11: THERMAL PROPERTIES OF MATTER
PreparedbyCg
EdnaMariaHjOsman.E-ma
il:[email protected]
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WHAT HAPPENS TO MATTER
WHEN THERMAL ENERGY IS
APPLIED TO IT?
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OF THE MATTER
THERMAL ENERGY
CAN
Changethe temperature
Changethe state
EdnaMariaHjOsman.E-mail:[email protected]
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WHAT DO WE KNOW?
When heat is applied to a substance.The substance may undergo changes of state.
Heat Energy Applied
Change in Stateof substance
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When heat is removed from a substance.The substance may undergo changes of state.
Heat Energy Removed
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FOCUSON
THESUBSTANCEmELTING&BOILING
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A change of state from solid to liquid without a
change in temperature.
SOLID LIQUID
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m.p = -117 C
Et
hly
Alc
oho
l
m.p = 0 C
Ice
m.p = 57 C
W
ax
For a puresubstance, melting
occurs at afixedtemperature.
This temperatureis known as
the melting point.
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m.p = 232 C
Tin
m.p = 1060 C
Gold
For a puresubstance, meltingoccurs at a
fixedtemperature.
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DETERMINATION OF MELTING POINT
The solid is slowly heated until all the solid melts.
EdnaMariaHjOsman.E-mail:edna.maria.osman@gmai
l.com
Procedures
Record the initial temperatureof the solid.1
Start heating with a slow
flame from a Bunsen burner.2
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Take readings of
temperature every minute
until all the solid has melted
and the temperature of the
liquid reaches a certaintemperature.
3
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Plot a graph of temperature
against time.4
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-10
0
10
20HEATING CURVE OF ICE
Tem
perature/
C
Time / min
The graph is a smooth curvewith a horizontal section.
Heating curves are used to
determine melting points.
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The horizontal lineindicatesa change of state.
Refer to the temperature
axis for the melting point!
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SOLIDIFICATION
A change of state from liquid to solid without a
FREEZING
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Napthalene
freezing pt = 79 C
Forapure substance,freezing occursat a
the freezing point.
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DETERMINATION OF FREEZING POINT
The liquid is slowly cooled until all the liquid freezes.
Record the initial temperature
of the liquid.1
Take readings of temperature
every minute until all the liquid
freezes and the temperature ofthe solid reaches a certain
temperature.
2
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Plot a graph of temperatureagainst time.
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65
70
75
80
85
90
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
COOLING CURVE OF NAPTHALENE
Temperature/
Cooling curves are used to
determine freezing points.
EdnaMariaHjOsman.E-m
ail:[email protected]
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axis for the freezing point!PreparedbyCg
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axis for the freezing point!
Freezing point isthe temperature atwhich a liquid changes to a solid.
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MELTING POINT & FREEZING POINT
A pure substance will solidify/ freeze at atemperature equal to its melting point.
Melting Point
of Substance
Freezing Point
of Substance=
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BOILING
A change of state from liquid to gas without a
LIQUID GAS
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For a pure substance, boiling occurs ata
the boiling point.
b.p = 35 C
Ether
b.p = 79 C
Alcohol
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b.p = 357 C
Mercury
b.p = 100 C
Water
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DETERMINATION OF BOILING POINT
1030
50
110HEATING CURVE OF WATER
Heating curves arealso used to determine
boiling points.
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These horizontal linesindicate
changes of state.
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Theupper horizontallinesindicateliquid to
gasconversion
Refer to thetemperature axisfor the boiling
point!
ail:edna.maria.osman@gma
il.com
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Thelower horizontallinesindicatesolid to
liquidconversion
Refer to thetemperature axisfor the melting
PreparedbyCgEdnaMariaHjOsman.E-m
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CONDENSATION
A change of state from gas to liquid without a
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BOILING POINT & CONDENSATION POINT
A pure substance will condense at a temperatureequal to its boiling point.
Condensation Point
Boiling Point of
Substance=
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WHY IS
THE TEMPERATURECONSTANT DURING
CHANGES OF STATE?PreparedbyCgEdnaMariaHjOsman.E-m
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LATENT HEATAll the thermal energy is used to break/create the
substances intermolecular bonds during changes of state.
SOLIDLIQUIDGAS
CreatingBonds
Breaking
Bonds
None of the thermal energy is used to change the kinetic
energy of the particles during changes of state.
There will be no change in the temperature of the substance.
SUMMARIZATION
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30
110
A HEATING CURVE
Te
mperature/
Boiling
Melting
Solid &
LiquidPresent
Liquid &Gas
Present
SolidPresent
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MELTING POINT & FREEZING POINTA pure substance will solidify/ freeze at a
temperature equal to its melting point.
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