The Particle Theory

Matter is anything that has mass and takes up space.

Anything around us and in the entire universe can be classified as either matter on energy.

The Particle Theory of Matter:

The particle theory of matter explains the following scientific phenomena:

  1.  Pure substance are homogeneous (one phase - one unique kind of particle)
  2.  Physical Changes - Melting, Evaporation, Sublimation, Dissolving.....
  3.  Characteristic Physical Properties - Density, Viscosity, Electrical & Thermal Conductivity


 B.        Properties:  Information about a substance that describe it and that helps us identify it.
Characteristic Physical Properties - are physical properties that can be used to identify a substance because they never change.  Example: The density of water is always 1.00 g/mL at room temperature.

 C.        States of Matter

Solid State
 rubber, iron, ice, chalk

Particles of a typical solid


Particles of solids are held in place by strong electrostatic forces and are densely packed together. Particles of solids vibrate constantly due to their internal energy but they cannot move from one place to another.  Particles of solids possess only vibrational energy.


Liquid State:
alcohol, gasoline, oil, water

Particles of a typical liquid
(What could the two different types of particles indicate?)


Particles of liquids are kept together by forces of attraction that are weaker than those of solid particles.  Within the walls of the  container they can move from place to place bumping into the sides of the container and into other particles.  This type of energy is called translational    energy.  This energy gives a liquid  the ability to flow and be poured and to spread when a liquid is spilled.  Liquid particles also have vibrational energy.


 Gaseous State:
Examples: air, natural gas, carbon dioxide, steam


Brownian Motion demonstrating possible motion of tiny solids particles suspended in air (a gas) and indirectly showing the motion of particles of gases.


Particles of gases are "more rarefied" than either liquids or solids.  This means that the forces of attraction that hold them together are very weak and that the spaces between them are much larger than the spaces between solid and liquid particles. Particles of gases can move  from  place to place within a container bumping against the walls of  the container and against other particles. They rotate and vibrate at the same time.  Particles of gases have rotational, translational and vibrational energy.  This explains why they can escape from a container very easily and they can put pressure on the side of the container (example a balloon or a tire).

D.        Physical Properties of Each State:







same as container (indefinite)

same as container (indefinite)




fills entire container (indefinite)

ability to flow




can be compressed

very slightly

very slightly


volume change with heating

very small



 E.         Describing Matter

 F.         How to Describe Matter (Qualitative & Quantitative Observations)

 G.        Chemical Properties:                

 Properties of a substance that we observe when it reacts or does not react with other substances

Physical & Chemical Changes

  Physical Change Chemical Change
  • No new substance is produced
  • Substance remains the same even with a change of state
  • May require addition of energy
  •  Release of energy may occur
  • Final substance is substantially different than initial substance
  • New substance is always produced
  • Energy is usually released but may be required to get the change going
  • Outside may look different
  • Inside remains the same
  • Particles may be rearranged
  • Forces of attraction between particles may be weaker or stronger
  • A new substance is produced
  • The particles of the new substance do not resemble those of the old substance
  • Internally, the substance produced is different than the old substances
  • Mixing sugar and water
  • Ice melts into water
  • Solid wax  ==>    Liquid wax
  • Vinegar and baking soda mix to form carbon dioxide
  • Hydrochloric acid reacts with magnesium metal to form hydrogen gas


When a state of matter gains or looses heat it undergoes a change.

A gain in heat is called an endothermic change.  A loss in heat is called an exothermic change.

The table below summarizes the six changes of states that matter can undergo and tells you if heat is added or removed for the change to take place.

Change From To Heat Examples
Sublimation solid gas or vapour added = endothermic Moth crystals disappear when left in a closet for several days
Sublimation gas or vapour solid removed =  exothermic frost forms on a car's windshield
Evaporation or vapourization liquid gas added = endothermic Rain dries up when the sun comes out
Melting or Liquefaction solid liquid added = endothermic
An ice cube turns into water when left out of the freezer
Freezing or Solidification liquid solid removed =  exothermic
A bottle of water will turn into ice if left in the freezer


gas or vapour liquid removed =  exothermic Drops of water form on the mirror when taking a hot shower

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