Explain how phase changes, kinetic theory and forces of attraction can be used to explain behavior of gases, liquids and solids?

The three common forms of matter on earth are solid,
liquid, and gas. The form that any substance is in depends on the relative motion of the
particles of the substance and the degree of attraction between the different
molecules.

Kinetic molecular theory says that are
constantly in motion unless the temperature is at absolute zero. This motion can be one
of two kinds - either internal motion due to the vibration of the molecules and atoms of
the substance - or translational meaning the individual atoms and/or molecules are free
to move in relation to one another.

Let's start with a
solid at relatively low temperature.  A solid remains a solid because the forces of
attraction within  the solid are strong and motion between molecules is essentially
zero.

Now start adding heat energy to the solid. As you do
so the energy is absorbed and the internal vibrations of the solid increase, and the
temperature of the solid increases.  Temperature being a measure of the average kinetic
energy of the solid.  Depending on the solid, this can happen for a long time before any
visible changes can be seen. Thus, if you heat a metal frying pan on a stove, it
obviously gets hotter, but not hot enough for the molecules to start moving and
melting.

Eventually, as you add more heat energy, the solid
will reach a point where it starts turning into a liquid.  This is called the melting
point and is a physical characteristic of every pure substance.  Now as you add more
heat energy, something interesting happens.  As long as the solid is melting, the
temperature remains constant and does not begin rising again until all of the solid has
changed into a liquid.  In the liquid state the internal motion of the atoms and/or
molecules has increased, the degree of attraction is less, and the atoms are able to
move in realation to each other.

Now continue adding heat
energy to the liquid, watching the temperature rise, until the temperature reaches the
boiling point.  When the boiling point is reached the atoms of the liquid are moving
fast enough that the attraction between them is broken and they escape from the surface
of the liquid into the air as a gas.  This phase change again happens at a constant
temperature until all of the liquid has been changed into a
gas.

All of this can be shown on a graph of energy on the
x-axis vs. temperature on the y-axis.  If you start at the origin you have a solid and a
sloping line upward as heat is added. At the melting point the line flattens, then rises
sloping upward as the liquid is heated, flattens again as it changes phase from liquid
to gas, then again slopes upward.