Solutions &
The Dissolving Process
LG: I can explain the behaviour of molecular
and ionic compound in water
Forces at Work
• Inter- and intramolecular forces can be used
to explain many of the properties of solutions
• Intramolecular forces
– Covalent bonds
– Ionic bonds
• Intermolecular forces
– Dipole-Dipole
– London Dispersion
– Hydrogen bonds
What makes water so special?
• It is often called the “universal solvent”
• Many substances, but not
all, dissolve in water
• Water is a good solvent
for 3 reasons:
– Small size
– polar
– Capable of hydrogen
bonding
Ionic Solutes in Water
• Ionic compounds have strong bonds and high
melting points but tend to dissolve easily in water
– Positive hydrogen atoms
are attracted to anions
Hydration
in ionic compounds
– Negative oxygen atoms
are attracted to cations
in ionic compounds
– The process of ions
separating from a crystal
is called dissociation
– Ex. NaCl(s)  Na+(aq) + Cl-(aq)
– Na2CO3(s)  2 Na+(aq) + CO32-(aq)
Molecular Solutes in Water
• Molecular compounds vary in their ability to dissolve
in water; it depends on whether the molecule is
polar and capable of hydrogen bonding
• If a molecular compound dissolves, the molecule
remains intact
Molecular Solutes (cont)
• Liquids that mix easily are said to be ‘miscible’
– Water and ethanol mix easily
because both are polar and
capable of hydrogen bonds
“Like Dissolves
Like”
• Liquids that do not mix easily are
‘immiscible’
– Oil and water do not mix because water
molecules are more strongly attracted
to each other
Surfactants & Emulsifiers
• Surfactants and emulsifiers both contain a polar end
and a non-polar end which help molecules with
different polarity mix
– Surfactants (for cleaning): soaps and detergents
– Emulsifiers (for cooking): egg and mustard
Activity: Psychedelic Milk!
• Materials:
– Detergent, milk, plate, food colouring, Q-tips
• Instructions:
– Add about 1cm of milk to the dish
– Put a few drops of different colours of food
colouring onto 3 spots on the surface of the milk
– Dip a Q-tip in detergents and place it somewhere
in the milk
Homework
Pg. 389 # 1 – 8, 12, 15