Atomic Theory of Matter
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What is Matter made of?
Our current theory of matter is that it is made of tiny particles called atoms.  These atoms are
too small to be seen, even with a microscope!  

These atoms can be arranged in two different ways:
  1. Elements - things made of only one type of atom so they cannot be broken down into
    smaller things.
  2. Compounds - things made of two or more types of atoms that are chemically combined.  
    This changes the properties of the compound to be different than the properties of the
    atoms they are made of.
The Phases of Matter
To understand the phases of matter (solid, liquid, gas) we need to know two rules.
  1. All particles of matter have some attraction to each other.  Some things have
    a HUGE attraction and some things have very little attraction.
  2. All particles of matter are moving.  This motion is called heat.  The more heat
    they have the more they are moving. (and conversely: the less heat they have the
    less they are moving. (If they could stand still then they would have no heat the
    temperature would be absolute zero)
Phases of Matter
Putting it all together
Remember:  
The attraction
between the
particles of water
does not change,
only the amount of
motion (heat)
changes.
Solids:
The energy is so low that the particles
stick together like tiny magnets.  This
means that they are just vibrating in
place.  They will not change their
shape because they are stuck in
place.  They cannot change their
volume because they are touching
and cannot get any closer.
Liquids:
There is enough energy to break
the bonds and the particles are
now sliding over each other.  They
can change their shape because
they are not fixed in place.  They
cannot change their volume
because they are touching and
cannot get any closer together.
Gases:
the particles fly away from each
other.  This means they will fly away
till they hit something.  In this state
they will take up the volume and
shape of the container that they
are in.  They can change their
volume because there are spaces
between them.