Solids,%20Liquids,%20and%20Gases

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Solids, Liquids, and Gases

• States of Matter

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Solids, Liquids, Gases

• Solids - Atoms and molecules vibrate in a
  stationary spot
• Liquids atoms and molecules move, but are still
  bound together
• Gases atoms and molecules move freely and
  bounce off one another without sticking together

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Forces that hold matter together

• Matter is held together by forces of attraction
• The forces of attraction must be strong enough to
  overcome the energy of atoms in motion
• For a substance to go from solid to liquid, or
  liquid to gas, forces of attraction must be
  overcome by motion of particles
• Higher melting and boiling points mean stronger
  forces

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Forces of attraction

• Strongest to weakest
• Chemical bonds
• Hydrogen bonds
• Dipole-dipole interactions
• London dispersion forces

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What makes a substance a solid, liquid, or gas?

• Strength of bonds
• Size of the molecule, if molecular
• Temperature
• Metallic substances and ionic substances (and
  some covalent substances) are bound together in
  large arrays with strong bonds solids under
  normal conditions

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Dipole Forces

• All three types of forces other than bonds are
  similar based on electric attraction
• All are based on dipole moments a positive end
  and a negative end of an atom or molecule
• Hydrogen Bonds are strongest
• Then permanent dipoles
• Then temporary dipoles London dispersion forces

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Solids

• Usually more dense than liquids
• Often have particles in a particular arrangement
  a crystal formation
• Crystals may be of many types
• Governed by electric forces could be ions,
  dipoles, hydrogen bonds
• Amorphous solids are those without a crystal
  structure

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Liquids

• In a liquid, molecules, atoms and ions can move
  freely (fluid), but are still attached to others
• The ease of flow is called viscosity
• Most substances flow more easily as the particles
  get warmer
• Surface tension is the force at the surface of
  the liquid

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Gases

• Gases are individual particles in motion, but not
  attached to others
• When they hit another particle, they bounce off
• The volume of the gas particles is small in
  relation to the total volume, so gases can be
  compressed, where solids and liquids cannot

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Phase Change

• When a substance is melted or boils, energy must
  be supplied
• When a substance condenses or freezes, energy is
  released
• This energy is called
• Heat of fusion (for melting and freezing)
• Heat of vaporization (for boiling and condensing)

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Deposition and sublimation

• In some conditions a substance may go directly
  from a vapor state to a solid state, called
  deposition
• Going from a solid state to a vapor state is
  called sublimation
• Vapor to solid is called deposition

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Vapor Pressure

• Even when below the boiling point, some molecules
  have enough energy to escape from a liquid
• These molecules exert a pressure, called the
  Vapor Pressure