Briefly explain what happens when you dissolve:
1. NaCl in water
2. Acetic acid in water
3. Ethanol in water
4. Polystyrene in Toluene
What does this tell you about the chemical bonding in each case?

1. NaCl in water (ionic bond in polar solvent)
Bond type: Hydrogen bond, ion-dipole
Salt is made up of sodium and chloride ions held together by ionic
bonds.  When sodium chloride breaks up, ionic bonds are broken. As the
sodium and chloride ions move between the water molecules, the
hydrogen bonds holding the water molecules together must also be
broken. Because water molecules are polar, they have a positive end
(H) and a negative end (O).
The positive ends of the water molecules are attracted to the negative
chloride ions and the negative ends of the water molecules are
attracted to the positive sodium ions. These attractions between ions
and polar molecules are called ion-dipole bonds. They are comparable
in strength to hydrogen bonds or maybe even a bit stronger. When an
ionic material, like salt, dissolves in water, both ionic bonds and
hydrogen bonds are broken and ion-dipole bonds are formed.
(http://dl.clackamas.cc.or.us/ch105-03/mixing2.htm)

2. Acetic acid in water (weak acid in water)
Bond type: hydrogen bonding, ion-dipole
When acetic acid is placed in water, the effect is that the molecule
dissociates into a proton (H+, but more accurately, a hydronium ion,
H3O+) and an acetate ion.  These ions form ion-dipole bonds with
water, allowing them to dissolve.  However, because acetic acid is a
weak acid, not all of the molecules dissociate (in fact, only about
4-5% do).  The rest remain in CH3COOH form.  Since the acetic acid
molecule has polar components (the O-H bond), hydrogen bonds are
formed with the polar molecules, allowing them to dissolve as well.

3. Ethanol in water (both polar molecules)
Bond type: hydrogen bond, ion-dipole
Ethanol, with a molecular formula of C2H5OH, does not dissociate like
acetic acid does.  The polar component of the molecule, O-H, allows
the molecule to form hydrogen bonds with water.  The oxygen atom in
the water molecule is attracted to the positive, hydrogen atom in
ethanol and the hydrogen atom in the water molecule is attracted to
the negative, oxygen atom in the ethanol.  (the charge is due to the
oxygen having a greater electronegativity, pulling the electrons from
the hydrogen towards itself, making itself more negative).  Once
again, ion-dipole bonds are formed, allowing ethanol to dissolve in
water.

Polystyrene in Toluene (both non-polar molecules)
Bond type: dispersion forces, induced-dipole
Both polystyrene and toluene are whole non-polar molecules.  Non-polar
molecules will dissolve in other non-polar molecules.  This is due to
the existence of dispersion forces (sometimes called london forces). 
Since the electrons are constantly moving around the molecules, there
exists and instant in time where the electrons are congregated more on
one side of the molecule then another.  This gives the molecule a
temporary charge, or, dipole. The positive end of the molecule
attracts the electrons of other molecules, and the negative end
repels.  This causes a ripple effect in the solution, causing more and
more more molecules to gain dipoles.  Though these dipoles last for an
extrememly short time, they are enough to create intermolecular
forces, allowing polystyrene to dissolve in toluene.

Search Strategies:
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I hope that helps, if you have any questions, feel free to ask for
clarification.

-Tox-ga

Very knowledgeable answer, good explaining.