heat changes
DESCRIPTION
Heat Changes. Enthalpy. E N T H A L P Y - H. heat content in matter:. E N T H A L P Y - H. heat content in matter: natural systems tend to go from a state of high energy to a state of low energy. E N T H A L P Y. The phases of matter represent "classes" of molecular motion found - PowerPoint PPT PresentationTRANSCRIPT
E N T H A L P Y - HE N T H A L P Y - HE N T H A L P Y - HE N T H A L P Y - H
heat content in matter:
E N T H A L P Y - HE N T H A L P Y - HE N T H A L P Y - HE N T H A L P Y - H
heat content in matter:
natural systems tend to go from a state of high energy to a state of low energy.
E N T H A L P YE N T H A L P YE N T H A L P YE N T H A L P Y
The phases of matterrepresent "classes" of molecular motion found at different temperatures.
E N T H A L P YE N T H A L P YE N T H A L P YE N T H A L P Y
The phases of matterrepresent "classes" of molecular motion found at different temperatures.
XKinetic Energ
y
E N T H A L P YE N T H A L P YE N T H A L P YE N T H A L P Y
The phases of matterrepresent "classes" of molecular motion found at different temperatures.
XHEAT
E N T H A L P YE N T H A L P YE N T H A L P YE N T H A L P Y
q = U + P Vq = heat gained or lostU = internal energyP = PressureV = volume
E N T H A L P YE N T H A L P YE N T H A L P YE N T H A L P Y
Hfus - heat of fusion
As energy is added to a solid at its melting point, ALL the energy is used to increase the kinetic energy of the molecules during the phase change.
E N T H A L P YE N T H A L P YE N T H A L P YE N T H A L P Y
Hfus - heat of fusion
The amount of heat needed to change one gram of a solid into a liquid at its melting point.
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Heat Added
Tem
per
atu
re R
ise
Every phase change isaccompanied by a changein the energy of the system.
As the temperature of a solidincreases, its particle vibration increases.
When a solid melts, itsparticles are freed to move with respect to one another.
This melting process is called fusion.
The increased freedom ofmotion of the molecules orions comes at a price...
measured by the heat of fusion, or enthalpy of fusion, Hfus
As the temperature of a liquidincreases, the molecules movewith increasing energy.
When increasing temperature,the concentration of gas-phasemolecules just above thesurface of the liquid increases.
These gas-phase moleculesexert a pressure on theliquid called vapor pressure.
This vapor pressure increases with temperature until it equals the atmospheric pressure.
This is the boilingpoint of the liquid.
The energy required tocause this transition..
is called the heat of vaporization or enthalpy of vaporization, Hvap
solid/liquid phase change
q = m Hfus
q = heat gained or lostm = massHfus = heat of fusion
E N T H A L P YE N T H A L P YE N T H A L P YE N T H A L P Y
Hfus H2O = 334 J/g
Hfus lead = 24.72 J/g
E N T H A L P YE N T H A L P YE N T H A L P YE N T H A L P Y
As energy is added to a liquid at its boiling point, ALL the energy is used to increase the kinetic energy of the molecules during the phase change.
E N T H A L P YE N T H A L P YE N T H A L P YE N T H A L P Y
Hvap - heat of vaporization
The amount of heat needed to change one gram of a liquid into a gas at its boiling point.
liquid/gas phase change
q = m Hvap
q = heat gained or lostm = massHvap = heat of vaporization
E N T H A L P YE N T H A L P YE N T H A L P YE N T H A L P Y
Hvap H2O = 2260 J/g
change temp within change temp within phasephase
q = m Cp
q = heat gained or lostm = mass= “change in temperature”
Cp = specific heat capacity
Specific Heat Specific Heat CapacityCapacity
Specific Heat Specific Heat CapacityCapacity
The heat required to raise
the temperature of onegram of a substance byone Celsius degree.
Specific Heat Specific Heat CapacityCapacity
Specific Heat Specific Heat CapacityCapacity
Cp of ice = 2.06 J/g.Co
Cp of water = 4.18 J/g.Co
Cp of steam = 2.02 J/g.Co
Cp of copper = .385 J/g.Co
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q=mHvap - change phase
q=mHFUS- change phase
q=mCp - change temp
q=mCp - change temp
q=mCp - change temp
Heat of Fusion of Ice
How much heat is needed toconvert 250 grams of ice at -30 oC to vapor at 150 oC?
1. Change temp of ice2. Melt ice3. Change temp of liquid water4. Vaporize water5. Change temp of vapor6. Add total heat used
Step 1 raise temp of ice
q = m T Cp
q = (250g) (30 Co) (2.06 J/g. Co)
q = 15,450 JoulesQuickTime™ and a
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Step 2 melt ice
q = m Hfus
q = (250g) (334 J/g)
q = 83,500 JoulesQuickTime™ and a
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Step 3 raise temp of liquid water
q = m T Cp
q = (250g) (100 Co) (4.18 J/g. Co)
q = 104,500 JoulesQuickTime™ and a
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Step 4 vaporize liquid water
q = m Hvap
q = (250g) (2260 J/g)
q = 565,000 JoulesQuickTime™ and a
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Step 5 raise temp of water vapor
q = m T Cp
q = (250g) (50 Co) (2.02 J/g. Co)
q = 25,250 JoulesQuickTime™ and a
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Step 6
q = 15,450 83,500 104,500 565,000 25,250
q = 794,000 JoulesQuickTime™ and a
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What is
Which has the greater?
Fe H2Oor
Specific Heat Capacity - 13 min
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is used to measure
heat change
Calorimetry - 13 min
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Specific Heat of a Metal
Lab Burners and BTUs
P h a s e D i a g r a mP h a s e D i a g r a m
A g r a p h s h o w i n g A g r a p h s h o w i n g t h e p h a s e s o f t h e p h a s e s o f m a t t e r a s t h e m a t t e r a s t h e y r e l a t e t o y r e l a t e t o t e m p e r a t e m p e r a t u r e a n d t u r e a n d p r e s s u r e . p r e s s u r e .
M a j o r p o i n t s o n a p h a s e d i a g r a m
M a j o r p o i n t s o n a p h a s e d i a g r a m
Normal Atmospheric PressureNormal Atmospheric Pressure
Triple pointTriple point
Boiling PointBoiling Point
Melting pointMelting point
Critical temperatureCritical temperature
101.325 kPanormal atmospheric pressure
TP Triple Point
Tb
Normal boiling point
Tm
Normalmelting point
Tc
Criticaltemperature
V a n d e r W a l l s A t t r a c t i o n
V a n d e r W a l l s A t t r a c t i o n
T h e f o r c e o f T h e f o r c e o f a t t r a c t i a t t r a c t i o n o n b e t w e e n b e t w e e n
m o l e c u l e sm o l e c u l e s
Calories in a Peanut