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Phase Changes and Heating Curves 2016.notebook
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October 14, 2016
Oct 61:47 PM
Phase ChangesEndothermic and Exothermic
Aim: To determine what is occurring on the molecular level during a phase change
Nov 65:51 PM
Phase ChangesAll phase changes occur at constant temperature. Therefore average kinetic energy remains constant.
The energy that is changing during a phase change is potential energy.
During a phase change, the heat added (PE increases) or released (PE decreases) will allow the molecules to move apart or come together.
Phase Changes and Heating Curves 2016.notebook
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October 14, 2016
Nov 65:51 PM
Phase Changes
Fusion (melting): solid to a liquid
Boiling (vaporization): liquid to a gas
Sublimation: solid to a gas
Solidification (freezing): liquid to a solid
Condensation: gas to a liquid
Deposition: gas to a solid
Oct 61:49 PM
Endothermic Phase Changes
1. Melting(fusion): s to l
2. Boiling(vaporization): l to g 5. Condensation: l to g
4. Freezing(solidification): s to l
3. Sublimation: s to g 6. Deposition: g to s
Heat absorbed causes the molecules to move farther apart by overcoming the intermolecular forces of attraction.
Heat released allows the molecules to move closer together and the intermolecular forces of attraction become stronger.
Exothermic Phase Changes
Phase Changes and Heating Curves 2016.notebook
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October 14, 2016
Oct 62:06 PM
Phase EquilibriumPhase equilibrium when two phases exist at the same time during a phase change.
Fusion and Solidification occur at the same temperature for a substance.
H2O (s) <> H2O (l)
Vaporization and Condesnation occur at the same temperature for a substance.
H2O (l) <> H2O (g)
Melting(fusion) >
< freezing(solidification)
< condensation
vaporization>
Nov 168:29 AM
Phase Changes and Heating Curves 2016.notebook
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October 14, 2016
Oct 61:49 PM
• Shows the temperature of each phase change. (flat line)
• Shows the boiling point and melting point of a substance.
• Can be used to determine the phase of matter at a given temperature.
• Can be used to determine if the substance needs more energy to melt (fusion) or boil (vaporize).
Heating and Cooling Curves
Oct 67:24 PM
A
C
ED
B
Phase Changes and Heating Curves 2016.notebook
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October 14, 2016
Oct 67:25 PM
1. At what temperature does the substance begin to melt?
2. What temperature does it boil?
3. At which section is the substance a solid? liquid? gas?
4. What sections of the graph have constant kinetic energy?
5. What sections of the graph have constant potential energy?
Oct 67:00 PM
Model 2: Temperature of a Substance as Heat is Added Over Time
Time increasing >
Temperature (C
)
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October 14, 2016
Oct 65:25 PM
Practice Problems
Oct 65:26 PM
Practice Problems
Phase Changes and Heating Curves 2016.notebook
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October 14, 2016
Oct 87:32 AM
Oct 87:31 AM