PREAP CHEMISTRY CHAPTER 10 THE STATES OF MATTER

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PRE-AP CHEMISTRY CHAPTER 10THE STATES OF
MATTER
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Kinetic theory- The tiny particles in all forms
of matter are in constant motion.
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Kinetic theory of gases- valid only at extremely
low density

• 1. A gas is composed of particles, usually
  molecules or atoms
• Hard spheres
• Negligible volume
• Particles are far apart
• No attractive or repulsive forces exist between
  particles

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2.The particles in a gas move rapidly in constant
random motion.
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3.All collisions are perfectly elastic.
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The average speed of an O2 molecule is 1656
km/hr!!!
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Kinetic energy (KE)- the energy an object has
because of its motionWhen a gas is heated, it
absorbs thermal energy. Some of this energy is
converted to KE to increase the motion of
particles.
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Average KE of a gas is proportional to the Kelvin
temperature. Particles at 200K have twice the KE
of particles at 100K.The Kelvin temp scale is
used because 0K (absolute zero) is the temp at
which all motion ceases.
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Gas Pressure- the result of simultaneous
collisions of billions of gas particles on an
object
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Atmospheric pressure-

• results from the collisions of air molecules with
  objects
• Decreases with an increase in elevation because
  the atmospheric gases are less dense

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Barometer- instrument used to measure
atmospheric pressure
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SI unit of pressure- pascal (Pa)Standard
atmospheric pressure 101.3 kilopascals (kPa)
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1 mm Hg pressure needed to support a column of
mercury 1 mm highStandard atmospheric pressure
1 atm1 atm 760 mm Hg 760 torr 101.3 kPa
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STP 1 atm and 0oC
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Avogadros Hypothesis- Equal volumes of gases at
the same temperature and pressure have equal
numbers of particles.
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Liquids and solids are condensed states of
matter.Liquids and gases flow.Particles of a
liquid are held together by weak attractive
forces.
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http//intro.chem.okstate.edu/1515SP01/Lecture/Cha
pter12/PLMPhase.html
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Vaporization- the conversion of a liquid to a
gas or vapor below its boiling point
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Evaporation-

• Vaporization in an open container
• Highest energy (hottest) particles escape,
  leaving the cooler ones behind
• Evaporation rate increases when heated
• Cooling process

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Vapor pressure(VP)-

• pressure produced in a closed container by vapor
  particles colliding with the walls
• As temperature increases, vp increases

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Dynamic equilibrium rate of evaporation
rate of condensation
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Boiling Point (BP)-

• The temperature at which the vp of the liquid
  equals the external pressure
• Normal bp bp at 1 atm
• Mountains low bp
• Pressure cooker high bp
• The temperature of a liquid never exceeds its bp.

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Melting Point (MP)-

• The temperature at which a solid changes into a
  liquid (vapor pressure of solid and liquid are
  equal)
• Vibrations are strong enough to overcome
  attractive forces
• Melting point freezing point
• Ionic solids high melting point (strong
  attractive forces)
• Molecular solids low melting point (weak
  attractive forces)

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Crystal-

• Atoms, ions or molecules are arranged in an
  orderly, repeating, 3-D pattern called a crystal
  lattice.
• Regular shape
• crystal systems (can be used to identify)

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Unit cell- smallest group of particles within a
crystal that retains the geometric shape of the
crystal
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CarbonCrystalline forms

• 1.diamond
• -tightly packed
• -dense
• -hard

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2.graphite -loosely packed -low density
-soft
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3.fullerenes- includes Buckminsterfullerene
(Buckyballs), a 60 carbon sphere
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Amorphous (non-crystalline form)4.soot
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Other amorphous solids Rubber, plastic,
asphalt, glass
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Liquid Crystals- flow like liquids but at certain
temperatures, may possess ordered crystalline
structure- consist of rod-shaped molecules
which may or may not be in layers -change
colors depending on temperature or electrical
charge
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Phase Changes---change of physical stateEx.
Melting, freezing, evaporation, condensation,
sublimation, deposition--The temperature of a
substance does not change during a phase change.
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Sublimation- Change of a solid to a gas without
going through the liquid phaseDeposition is the
opposite Ex. Iodine, ice cube shrinkage,
freeze drying, freezer burn
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Phase Diagrams- A plot of temperature vs.
pressure, showing the state of matter that is
stable under each set of conditions
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The Phase Diagram for Water
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Diagrams of Various Heating Experiments Describe
the changes occurring in each experiment.
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The Phase Diagram for Carbon Dioxide
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Triple Point- temp and pressure at which the
gas, liquid, and solid phase all exist in
equilibrium
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Critical Temperature- temp above which the vapor
cannot be liquefiedCritical Pressure- pressure
required to change the vapor to a liquid at the
critical tempCritical Point- Critical temp and
critical pressure
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Energy and Phase Changes-Heat of fusion-
amount of heat required to melt one gram of a
solid at its melting point.For H2O 80 cal/g
or 6.01 kJ/mol
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Heat of solidification- amount of heat given up
as one gram of liquid changes to a solid at its
melting point heat of fusion
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Heat of vaporization- amount of heat required to
change 1 g of a liquid to a gas at its boiling
point at 1 atm.For H2O 540 cal/g or 40.7
kJ/mol
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Heat of condensation- amount of heat released
when 1 g of a gas condenses to a liquid at its
BP. heat of vaporization
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