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Copyright©2000 by Houghton Mifflin Company. All rights
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1
Chapter 13States of Matter
Gases, Liquids
and Solids
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2
Figure 10.1
Schematic Representations of the Three States of Matter
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3
• INDIVIDUAL MOLECULES FAR APART
• PARTICLES INTERACTING VERY LITTLE
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• MOLECULES ARE VIRTUALLY LOCKED IN PLACE
• CAN VIBRATE ABOUT THEIR POSITIONS
• VERY ORGANIZED
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5
• MOTION OF MOLECULES IS INCREASE
• GREATER MOVEMENT
• GREATER DISORDER
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6
Kinetic Molecular Theory
• Postulates
• A gas consists of a collection of small particles traveling in straight-line motion and obeying Newton's Laws.
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7
• Postulates
• The molecules in a gas occupy no volume (that is, they are points).
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8
• Postulates
• Collisions between molecules are perfectly elastic (that is, no energy is gained or lost during the collision).
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9
• Postulates
• There are no attractive or repulsive forces between the molecules.
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• Postulates
• The average kinetic energy of a molecule is
3/2 kT
• T is the absolute temperature.
• k is a constant
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11
• http://www.chm.davidson.edu/vce/kineticmoleculartheory/basicconcepts.html
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12
Liquids
• Particles in a liquid are attracted to each other.
• More dense than gases
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13
Some Properties of a Liquid
Surface Tension: The resistance to an increase in its surface area (polar molecules).
Capillary Action: Spontaneous rising of a liquid in a narrow tube.
Viscosity: Resistance to flow (molecules with large intermolecular forces).
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14
Liquids
• Conversion of a liquid to a gas is called vaporization.
• Evaporation versus Boiling?
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15
Surface Tension
• UNEVEN PULL OF MOLECULES AT THE SURFACE
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16
Figure 10.6
Molecules in a Liquid
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17
Liquids
• Vapor Pressure:
Measure of the force exerted by a gas above a liquid.
Increasing Temperature increases vapor pressure.
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18
Solids
• Generally described as
an orderly arrangement of particles
in fixed positions.
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19
Types of Solids
Crystalline Solids: highly regular arrangement of their components
Amorphous solids: considerable disorder in their structures (glass).
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Crystalline Solid
Lattice: A 3-D system of points designating the centers of components that make up the substance.
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Unit Cell
Smallest repeating unit of the lattice.
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Crystalline Solid
Unit Cell: The smallest repeating unit of the lattice.
Three common types:
simple cubic body-centered cubic face-centered cubic
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23
Figure 10.9
Three Cubic Unit Cells and the Corresponding Lattices
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24
Figure 10.12
Examples of Three Types of Crystalline Solids
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Allotropes
• Two or more different forms of the same element in the same physical state.
• Allotropes of carbon: diamond, graphite and buckminsterfullerene
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Diamond
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Graphite
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Buckminsterfullerene
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29
• http://preparatorychemistry.com/KMT.html
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30
To answer that we need to know more
about
Gas Pressure.
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31
Pressure
• Force per unit area
Pressure
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32
Gases.
The gas molecules are in constant motion, and sothey regularly hit the walls of the container.
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Gases.
The force of the gas molecules hitting the walls of the container is called the Gas Pressure.
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34
Gases.
The more gas molecules there are, the more often thewalls of the container are hit,
therefore the Gas Pressure is higher.
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35
Gases.
If the temperature (energy) of the gas is increased the molecules move faster and so hit the walls harder
causing the Gas Pressure to rise also.
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36
Measuring Pressure.
Vacuum. Vacuum.
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37
Measuring Pressure.
Vacuum.Gas Pressure.
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38
Measuring Pressure.
Vacuum.Gas Pressure.
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39
Measuring Pressure.
Pressure is enough to push 20 cm/H2O………or 10 mm/Hg……..
Manometer.
Vacuum.Gas Pressure.
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40
Spaceis a vacuum.
Atmosphere isa gas (Air).
Air moleculeshit the surface ofthe earth.
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41
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42
Atmospheric Pressure
Pressure of the Airmolecules hitting
the earth.(or any other surfacein the atmosphere).
14 lbs. per square inch
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43
Atmospheric Pressure.
Patm = 760 mm/Hg (compared to a vacuum).
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44
We are so accustomed to Atmospheric Pressure that we forget its there.
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Atmospheric Pressure = Weight of the Air
Results from the mass of the air beingpulled toward the center of the earth by GRAVITY.
Measures using a barometer.
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46
Figure 5.2A Torricellian Barometer
At sea level =760 mm Hg
At elevation of 9600 feet =
520 mm Hg
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47
Pressure
is equal to force/unit area
SI units = Newton/meter2 = 1 Pascal (Pa)
1 standard atmosphere = 101,325 Pa
1 standard atmosphere = 1 atm =
760 mm Hg = 760 torr
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Pressure Units
• 1 atmosphere (atm)= 760 mm Hg= 760 torr= 101,325 Pa= 29.92 inch Hg= 14.7 lb/ in2 (psi)
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49
CHANGES OF STATE (PHASE TRANSISTIONS)
1) MELTING: s l
2) FREEZING: l s
3) VAPORIZATION: l g
4) SUBLIMATION: s g
5) CONDENSATION: LIQUEFACTION: g lDEPOSITION: g s
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50
PHASE DIAGRAMS
• GRAPHICAL WAY TO SUMMARIZE THE PHASES OF A SUBSTANCE AS A FUNCTION OF TEMPERATURE ANE PRESSURE
• DIAGRAMS NOT DRAWN TO SCALE
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51
The Phase Diagram for Water
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52
Figure 10.52
The Phase Diagram for Carbon Dioxide
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53
TRIPLE POINT
• REPRESENTS TEMPERATURE AND PRESSURE AT WHICH 3 PHASES OF A SUBSTANCE COEXIST IN EQUILIBRIUM
• FOR WATER,– 0.016 °C, 0.00603 atm (0.61 kPa).
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54
CRITICAL POINT
• CRITCAL TEMPERATURE:TEMPERATURE ABOVE WHICH
THE VAPOR CANNOT BE LIQUEFIED NO MATTER WHAT PRESSURE IS APPLIED
• CRITICAL PRESSURE:VAPOR PRESSURE AT THE
CRITICAL TEMPERATURE• WATER: 374°C, 218 atm.