Particle Theory Of Matter by liaoqinmei


Theories and Models

 Scientists use theories and models to try to
  explain why things work the way they do.
 A “good” theory can be used to predict
  certain events in the system
 If the theory constantly predicts the behavior
  of a system and what happens, then it is
  accepted as accurate
Particle Theory

 This is a model we use to try to explain how
  matter behaves
 This theory is over 100 years old
 Remember that matter is the “stuff” that
  makes up a substance
Particle Theory Cont

 The basic units of matter are atoms and
 Atoms
   the smallest particle of an element that can exist
    either alone or in combination
 Molecules
   the smallest particle of a substance that retains all
    the properties of the substance and is composed
    of one or more atoms
What the Theory Says
   All Matter is made up of small particles.
    These particles are so small that literally billions of them fit on this dot "."
   All particles of a pure substance are identical. For example ice, water and water
    vapour are all made of H20 and each particle (molecule) of each (ice, water ...)
    have the exact same MASS and VOLUME.
   The particles in matter are "attracted" to each other. This attraction becomes
    stronger as the particles get closer to each other ! This explains why solids are
    more rigid than liquids (Solids are usually denser than liquids).
   The spaces between the particles are HUGE compared to the size of the actual
   The particles in matter are ALWAYS IN MOTION. The speed of the particles
    depends on the temperature. When particles are HOT they have MORE energy
    and are moving faster than cold particles. The motion of particles causes them to
    bump around and bounce off each other.

 In Solids the particles
  are moving slow (they
  vibrate) and the
  particles in the solid do
  NOT have enough
  energy to overcome
  the attractive forces
  between them.
 We call this a lattice

 In Liquids the particles
  are moving fast
  enough to move
  around each other but
  they do NOT have
  enough energy to
  overcome the
  attractive forces
  between them

 In Gases, the particles
  are moving so fast that
  they have enough
  energy to overcome
  the attractive forces
  between them

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