Phases of matter: Comparison

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Phases of matter Comparison
Property Solid Liquid Gas
Particles Closely packed High density (ButWater is different!) More densely packed than in gas Most compressible-least densely packed
Particle movement Vibrate weakly around fixed positions Lowest kinetic energy Can change positions with other particles Can change positions with other particles Highest kinetic energy
Intermolecular forces Most effective (strongest) Stronger than in gases Least effective (weakest)
Shape and volume Both definite Definite volume only No definite shape or volume
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Surface tension

• Force that pulls adjacent parts of a liquid
  surface together.
• The higher the attractive forces between
  particles in the liquid, the higher the surface
  tension.
• Hydrogen bonds make water have higher surface
  tension than most liquids.

Soap
Water droplet
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Solids

• Crystalline solids Particles are arranged in an
  orderly, geometric, repeating pattern.
• Examples Emerald, diamond, calcite
• Amorphous solids (Without shape)
• Particles are arranged randomly.
• Examples Glass, plastic

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Changing states

• Equilibrium When there is no net change in a
  system.
• Dynamic equilibrium
• When a vapor is in equilibrium with its liquid as
  one molecule leaves the liquid to become a vapor,
  another molecule leaves the vapor to become a
  liquid. In other words, an equal number of
  molecules will be found moving in both
  directions.

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LeChâteliers Principle

• When a system at equilibrium is disturbed by
  application of stress, it attains a new
  equilibrium position that minimizes the stress.
• "If stress is applied to a system at
  equilibrium,the system will tend to readjust so
  that the stress is reduced."

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Boiling Point

• Vapor pressure Pressure exerted by a vapor
  Pressure of the liquid at given temperature
• Liquid boils when its vapor pressure equals
  pressure of the atmosphere.
• Boiling is the conversion of a liquid to vapor
  within the liquid as well as at its surface.
• Boiling point is the temperature at which the
  equilibrium vapor pressure of the liquid equals
  the atmospheric pressure.
• Volatile liquids are liquids that evaporate
  readily.

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Boiling Point, cont.

• High elevation Low atmospheric pressure
• Low atmospheric pressure lower boiling point
• High pressure in pressure cooker increased
  boiling point, faster cooking
• If pressure above liquid increases, the liquid
  temperature rises until it matches the new
  pressure and boils again.

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Separation by Distillation

• Distillation is the separation of liquid
  substances according to their different boiling
  points.
• As a liquid mixture is heated, the substance with
  the lower boiling point will vaporize first.
• Distillate Condensed liquid substance

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Kinetic Energy and Equilibrium Vapor Pressure

• In the beginning
• particles condensing to liquid phase
• particles evaporating to gas phase
• Increase temp Increase kinetic energy
• Now, more molecules have enough energy to leave
  the liquid.
• More vapor molecules higher vapor pressure
• Equilibrium will soon be established, but at a
  higher vapor pressure.

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Phase DiagramA phase diagram is a graph of
pressure vs. temperature that shows the
conditions under which phases of matter exist.
Critical temp (Tc) Above this, the substance
cannot exist in the liquid state.
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Four major "points" on a phase diagram

• Triple point, TP - All three phases can exist in
  equilibrium at this temperature and pressure.
• (The solid-liquid line and the liquid-vapor line
  meet.)
• Normal boiling point, Tb - The temperature at
  which the vapor pressure of a liquid is equal to
  standard atmospheric pressure.
• (Standard atmospheric pressure line crosses the
  liquid-vapor line.)
• Normal melting point, Tm - The temperature at
  which the vapor pressure of the solid and the
  vapor pressure of the liquid are equal.
• (Standard atmospheric pressure line crosses
  the solid-liquid line.)
• Critical temperature, Tc - The temperature above
  which no amount of pressure will liquefy a vapor.
  
• (The liquid-vapor line becomes vertical.)