The Boring States of Matter CH11

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The Boring States of Matter CH11
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Kinetic Energy EK

• The energy an object has because of its motion.
• Temperature is a measurement of average kinetic
  energy.

• Kinetic Theory-
• Tiny particles in all forms of matter are in
  constant motion.

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Liquids vs. Gases

• Liquids, the molecules are moving and touching.
• They interact
• They take up less space than gasses
• They overall have less Ek than a gas of the same
  substance

• Gases, the molecules bounce off each other, but
  do not stay in contact
• There is very little interaction between
  molecules
• They take up a lot of space

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Which of these 2 parts are compressible? Can you
squish the gas? Can you squish the liquid?
 
gas
liquid
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Evaporation conversion of a liquid to a gas

• At the surface, there are a few molecules that
  have enough Ek to escape to gas.
• By increasing the temperature, more molecules
  will have the necessary Ek and evaporation will
  occur faster than before.

The vapor pressure increases with more heat/ Ek
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Average kinetic energy

• Temperature is a measurement of average kinetic
  energy.
• If a beaker of water reads 20C, do all molecules
  in the beaker have kinetic energy 20C?

There is a broad range of kinetic energies. Most
of the molecules are around 20C, but there are
some significantly less energetic, and some
significantly more energetic.
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Solids

• Molecules in solids only vibrate in place, they
  do not slide past each other
• They interact in their FIXED position
• More dense than gas, and most liquids

Salt crystal, atoms are in a set position
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Heating a solid

• S ? L melting
• L ? S freezing
• L? G vaporization (or evaporation)
• G? L condensation

• The vibrations increase
• If they vibrate enough, some of the bonds holding
  the solid together will break.
• This is called the melting point.

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Evaporation vs. Boiling point
Atm is pressing down on the surface
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Solid to a Gas?Sublimation

• Solids also have a vapor pressure.
• When vapor pressure is high enough, the solid
  will go to gas, without stopping at liquid.
• This is called sublimation.
• Gas to a solid
• DEPOSITION

Dry ice, is a classic example of sublimation
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Phase Transition names
Give the change of state for each term

• S?L
• L?S
• L? G
• G?L
• S? G
• G?S d

• Melting
• Freezing
• Vaporization
• Condensation
• Sublimation
• deposition

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Ionic Solids

• Strong forces between oppositely charged ions.
• HIGH melting points
• HIGH boiling points
• Non conductors as solids, conductors while
  molten.
• Often water soluble
• Depends upon attractive forces for each other and
  other molecules.

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Molecular Combination of 2 or more non metals

• Molecular substances have 3 important types of
  weak intermolecular forces
• Dispersion Forces
• Dipole Forces
• Hydrogen bonds

• Inter-molecular (between molecule) forces are
  weak.
• Therefore easy to separate
• Have low melting and boiling points
• Think Oxygen and Water
• Theyre gases and liquids at room temperature
• Non-Conductors of electricity

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Dispersion (London) Forces
Think of the electron cloud being agitated

• Most common type of intermolecular force.
• Caused by temporary induced- dipoles formed in
  adjacent molecules.

• All molecules have dispersion forces, the
  strength depends on 2 factors
• The of electrons in the molecule
• As molar mass increases, dispersion forces become
  stronger, the boiling pt of non-polar molecules
  increases.

F2 -188 Cl2 -34 Br2 59 I2 184
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Dipole Forces

• Electrically attractive forces between and
  end of adjacent polar molecules.

• Boiling points of
• N2 -196C
• O2 -183C
• NO -151C
• The Nitrogen Monoxide is slightly polar and
  therefore has weak dipole forces. This explains
  the relatively higher melting points.

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Hydrogen Bonding

• Unusually strong DIPOLE forces.
• This is due to the very small Hydrogen atoms
• Electronegativity difference with
• F fluorine
• O oxygen
• N nitrogen

• The strongest of the weak forces

Water H2O bp 100 C, H2S -61C
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Ek ½ x mass x velocity2
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Kinetic Theory and Gases

• A gas is composed of particles
• Small spheresno real volume for each particle
• The gas particles move in constant random motion
• Very fast ( 1000 mph), straight line until
  collision occurs
• All collisions are perfectly elastic
• No Ek is lost in the collision

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Gas Pressure

• Moving bodies exert force when they collide with
  other bodies.
• The result of the billions of particles colliding
  is gas pressure

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Atmospheric pressure (Atm)

• Gravity holds air molecules in the atmosphere
• Atm is the result air colliding with objects
• The average pressure under all that air is 1
  atmosphere.

Pressure Force Area
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Air Pressure

• Barometer created by Evangelista Torricelli in
  1646 
• Inverted a tube filled with mercury into a dish
  until the force of the Hg inside the tube
  balanced the force of the atmosphere on the
  surface of the liquid outside the tube 

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ATM and pressure

• The average height of the column at sea level was
  760millimeters of Mercury or
• 760mmHg
• We later gave this average pressure the name
  TORR, for Torricelli

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3 Ways to express measures of pressure

• Millimeters of Mercury (or Torr)
• mmHg, Torr
• Atmospheric Pressure Units
• Atm
• Pascal (or KiloPascals) we dont use this unit
• Pa, or kPa
• 760 mmHg 1.0 atm 760 Torr

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Convert the following pressure measurments

• 720 Torr to atm.

• 1.45 atm. to mmHg

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Putting it all together

• How can you know if a substance will melt, or
  sublimate?
• The transitions depend upon both pressure and
  temperature.
• At a given Temperature T
• At a low pressure, something might sublimate, at
  a higher pressure it would likely melt

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Phase diagram
liquid
solid
Pressure
Triple point, all 3 phases exist simultaneously
gas
temperature
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Phase Diagram for Water
Triple point .006 atm .001C
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4th state of matter Plasma

• Plasma
• Occurs at super hot temperatures
• Gas atoms are stripped of their electrons
• Mix of loose electrons, and gas ions is called
  PLASMA

• Hot plasmas make up the stars, and can be 10
  million degrees
• Not very relevant to HS Chemistry.

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Maxwell-Boltzman Distrubution
At high T More molecules are in a higher energy
state