Kinetic Theory

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Kinetic Theory
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States of Matter

• Liquid
• Solid
• gas

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How are these states of matter alike and
different?
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Kinetic Theory

• An explanation of how particles of matter behave

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3 assumptions of Kinetic Theory

1. All matter is composed of small particles (atoms,
   molecules or ions)
2. The particles are in constant, random, motion
3. These particles are colliding with each other and
   the walls of their container

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Thermal Energy

• Total energy of a materials particles including
• Kinetic energy vibrations and movements between
  the particles
• Potential energy resulting from forces that act
  within the particles

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Temperature

• A term commonly used to describe how hot or cold
  an object is

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• However, in science Temperature means the average
  kinetic energy of particles in the substance

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Average Kinetic Energy

• How fast the particles in a substance are moving

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• Molecules of frozen water at 0C move much
  slower than molecules of water at 100C.
• Molecules have a kinetic energy at ALL temps,
  including absolute zero, -273.15C
• At the temp, though, particle motion is so slow
  than no more thermal energy can be removed

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Solid State

• Particles are tightly packed in a specific
  ordered geometric arrangement
• Particles are strongly attracted to one another
• Molecules are still moving vibrating in place

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Liquid State

• Particles move faster than those in a solid
• This extra energy allows for them to partially
  overcome their attractive forces
• They have enough energy to break away from their
  ordered arrangement in a solid

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• Particles can slide past one another, allowing
  for liquids to flow and take the shape of their
  container

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• Since particles do not have enough energy to
  completely overcome their attractive forces they
  cling together, giving a definite volume

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Melting point

• Temperature at which a solid begins to liquefy
• As particles are heated they move faster
• They bump into one another and transfer their
  energy to adjacent molecules
• When particles of a solid gain enough kinetic
  energy to slip out of their ordered arrangement
  the solid melts

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Heat of Fusion

• The amount of energy needed to change a substance
  from the solid to the liquid phase.

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Gases

• Particles have enough kinetic energy to
  completely overcome the attractive forces between
  them

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• Gases do not have a fixed volume or shape

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Vaporization

• When liquid particles are moving fast enough to
  overcome their attractive forces and enter the
  gas state
• There are two modes of vaporization
• Evaporation
• boiling

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Evaporation

• Can occur at a temp below the boiling point
• Only occurs on the surface of a liquid
• Particles have enough energy to break away from
  the liquid

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Boiling

• Occurs at a specific temp
• Also depends on the pressure on the liquids
  surface
• Occurs throughout the liquid

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• There is an external pressure (air) pushing down
  on the surface of the liquid
• The force of this pressure keeps the liquid
  particles from escaping
• Boiling Point the temp when the pressure of the
  vapor in the liquid is equal to the external
  pressure

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• Gas particles move about randomly
• The movement of gas particles and the collisions
  between them cause gases to diffuse

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Diffusion

• Spreading of gas particles throughout a given
  volume until they are equally distributed

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Heating curve of a liquid

• All particles of water at -20 are in the solid
  state
• If heat is applied, the temp increases to 0
  where the ice begins to melt
• Once the ice begins to melt the temp stays
  constant until ALL ice is melted.
• All energy is put into overcoming the attractive
  forces in the solid

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• Once the ice is ALL melted, the particles are all
  moving freely and their avg kinetic energy begins
  to increase

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• When the temp reaches 100C the liquid begins to
  boil
• The temp will remain constant until ALL of the
  liquids particles have overcome their attractive
  forces

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Plasma

• Matter consisting of positively and negatively
  charged particles
• Overall charge is neutral due to equal number of
  each
• Particles are moving SO fast that when they
  collide they strip atoms of electrons

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• Most common state of matter in the universe
• Also found in lightening blots, neon and
  fluorescent tubes and auroras

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• Thermal Expansion
• When heated particles move faster
• As they speed up they move farther apart
• Also, when cooled, particles slow down and the
  attractive forces are stronger causing the
  particles to come closer together shrinking of
  an object

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Expansion in Liquid

• Thermometers the liquid inside expands when
  heated
• This causes it to fill more of the narrow tube

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Expansion in gases

• Hot air balloons the particles of heated air
  inside the balloon move faster and spread apart
• This makes the density of the air in the balloon
  less than the density of the cooler air outside
  of the balloon
• The balloon then rises

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Water

• Water works oppositely it expands when cooled
  and shrinks when heated
• Water is a polar molecule (means it has positive
  and negative poles)
• These charged regions affect the behavior of water

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• When the water cools and the molecules slow down
  they become more attractive and move closer
• Because of the positive and negative charges they
  can only arrange themselves in a specific manner
• Pos and neg charges will line
• This results in spaces or gaps

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• The empty spaces are larger in solid ice than
  liquid water
• This results in a lesser density and why ice
  floats

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Density of Different forms of Water
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Amorphous solids

• No exact temp where phase change occurs (boiling
  point)
• Soften and gradually turn into a liquid over a
  temp range
• Due to irregular particle arrangement. Jumbled
  chains and not neat geometric arrangements

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Amorphous solids
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Liquid crystals

• Normally the ordered geometric structure of a
  solid is lost when it becomes a liquid and gas
• Liquid crystals begin flowing like a liquid when
  they melt BUT they keep their geometric order

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Liquid Crystals