Ch 9
Section 2
States of Matter
Solids
  Particles packed closely together and constantly
vibrating
  Fixed volume
  Fixed shape
  Ex: Rock
Liquids
  Particles can slide past one another
  Definite volume
  No definite shape
  Ex: Liquid water
Gas
  Particles are far apart and attractive forces are
weak.
  No definite volume
  No definite shape
  Ex: Air you breath
Plasma
  Matter consisting of positively and negatively
charged particles
  No definite shape
  No definite volume
  Most common state of matter in the universe
  Ex: Sun
Melting
  The temperature at which solids begin to melt is
called the melting point
  Heat of fusion- energy required to change 1kg of a
substance from a solid to a liquid.
Freezing
  As a liquids temperature lowers the attractive
forces of a liquid are strong enough to place the
atoms in an ordered arrangement.
  The particles slow down enough so that the particles
are able to come together and become a solid.
Vaporization
  The energy of a liquid increases and some of the
particles have enough energy to overcome the
attractive forces between particles to change from a
liquid to a gas.
  Vaporization that occurs at the surface is called
evaporation.
Boiling
  Occurs at certain temperature
  Boiling point is the temperature at which the
pressure of the vapor in the liquid is equal to the
external pressure acting on its surface.
  Heat of vaporization- the amount of energy
required for 1 kg of the liquid at its boiling point to
become a gas.
Condensation
  When gas cools down to become a liquid.
  Ex: the water vapor in the air cooling and forming
water droplets on a cold glass or soda can.
Thermal expansion of solids
  As the temperature of a solid increases the
molecules vibrate more and the attractive forces
holding the solid together get weaker; this causes
the material to expand.
Thermal expansion in
liquids
  As the temperature in a liquid increases the
substance will expand.
Thermal expansion of gases
  As the temperature of a gas increases it expands.
  As the gas expands it becomes less dense.