Effects of Solutes in
Solution
 Define: boiling point, freezing point and electrolytes.
 Explore the effect of solutes on the boiling point and freezing
point of solutions (colligative properties).
 Describe the behavior of electrolytes in a solution.
Essential Questions
1. What effects do solutes
have on the boiling and
freezing points of
solvents?
Aim
How do solutes
affect the
properties of the
solution?
Key Words
2. What forces are
responsible for these
effects?
3. How does the presence of
electrolytes affect a
solution?
boiling point, freezing
point, elevation,
depression, ions,
electrolytes,
conductivity
What is the Boiling Point
of Water at STP?
B.P. (Boiling Point) = __________
H2O
F.P. (Freezing Point = _________
Predict what
happens to the B.P.
and the F.P. of water
when NaCl is added?
F.P. _______
B.P. _________
Boiling Point Elevation
Recall
Boiling is transition between two states of matter
Recall the following concept covered last semester:
what attractions/forces are responsible for states of
matter.
Intermolecular Forces!
Examples of
Intermolecular forces
What kind of intermolecular forces are at
play between NaCl and H2O?
___________________________________
____
Molecule-Ion Attraction
The intermolecular force
between NaCl and water are
very strong and therefore, very
hard to break.
How is this related to the
boiling point elevation of the
solution?
_____________________________
__
Freezing Point Depression
Hint: Solids Consist of a
Rigid Crystalline Structure
Why does the presence of solutes lower the
freezing points of solvents?
Solutes Get in the Way!
 When solutes are present, it becomes more difficult
for water molecules to connect with each other in
order to form a rigid solid shape.
 Also, solutes interact with solids to dissolve the solid.
In the same way that water dissolves solutes,
solutes dissolve ice (example: NaCl).
Complete the Following
Dissolving “Reactions”
A. C12H22O11(s) + H2O(l)  __________________________
1. How many different particles will be “floating” in
water? Which one(s)?
_____________________________________________
Deduction Question
A. NaCl(s) + H2O(l)  __________________________________________
1.
How many different particles are “floating” in solution? Which one(s)?
_____________________________________________________________________________________
B. CaCl2(s) + H2O(l)  _________________________________________
1.
In how many parts does CaCl2 break up? Which one(s)?
_____________________________________________________________________________________
C. From NaCl and CaCl2, which salt do you predict will be more effective in
melting the snow? Explain? ________________________________________________
____________________________________________________________________________
Hypothesize!
According to your answers to the previous question, what
conclusion can be drawn? Explain.
_______________________________________________
_____
_______________________________________________
Hypothesize!
What conclusion can be drawn from the diagram?
_________________________________________________________
_________________________________________________________
Notes
IV. Effects of Solute on Solvent Properties
A. Boiling Point Elevation – a rise in boiling point of a
solution caused by the presence of solutes (ex.
addition of antifreeze to car radiators to prevent the
water from boiling).
B. Freezing Point Depression – a lowering of the freezing
point of a solution caused by the presence of solutes
(ex. using salt to melt ice).
C. Colligative Properties – Properties that depend on
the number of solutes and the nature of the solvent
but NOT on the identity of the solute.
i. Boiling point elevation and freezing point
depression are colligative properties.
ii. The more particles of solute a solution contains,
the more the affect on boiling & melting points.
Number of solute  :
B.P. of Solvent 
: F.P. of Solvent 
Does Water
Conduct
Electricity?
Can we add something to
the water to make it
conduct electricity?
If so, what can we add?
NaCl
v.s.
Sugar
Does solid NaCl Conduct
Electricity by itself,
without water?
What happens in the
dissolving of sodium that
allows it to conduct
electricity in solution?
Notes
D. Conductivity – conductivity of electrical
current by a solution caused by the
presence of electrolytic solutes.
1. Electrolytes – are solutes that
dissociate/ionize (separate into ions) in
water and are therefore, able to conduct
electricity in solution form (Ex: Salts).
2. Electricity - the flow of charges (such as
ions in solution or electrons in metallic
bonds).
Video
Electrolytes Animation
http://youtu.be/aELPrWzixeU
Learning Check
1. When ethylene glycol (an antifreeze) is added to
water, the boiling point of the water
a. decreases, and the freezing point decreases
b. decreases, and the freezing point increases
c. increases, and the freezing point decreases
d. increases, and the freezing point increases
2. Which solution will freeze at the lowest
temperature?
a. 1 mol of sugar in 500 g of water
b. 1 mol of sugar in 1000 g of water
c. 2 mol of sugar in 500 g of water
d. 2 mol of sugar in 1000 g of water
Learning Check
3. A 1-Kilogram sample of water will have the highest
freezing point when it contains
3. 1 x 1017 dissolved particles
4. 1 x 1019 dissolved particles
c. 1 x 1021 dissolved particles
d. 1 x 1023 dissolved particles
4. At standard pressure, an aqueous solution of sugar
has a boiling point
a.
b.
c.
d.
greater than 100°C and freezing point greater than 0°C
greater than 100°C and freezing point less than 0°C
less than 100°C and a freezing point greater than 0°C
less than 100°C and a freezing point less than 0°C
5. Which solution containing 1 mole of solute dissolved
in 1000 grams of water has the lowest freezing point?
a. KOH(aq)
b. C6H12O6(aa)
c. C2H5OH(aq)
d. C12H22O11(aq)
Notes
Effects of Solutes on the Properties of Solvents
Notes
IV. Effects of Solute on Solvent Properties
A. Boiling Point Elevation – a rise in boiling point of a
solution caused by the presence of solutes (ex.
addition of antifreeze to car radiators to prevent the
water from boiling).
B. Freezing Point Depression – a lowering of the freezing
point of a solution caused by the presence of solutes
(ex. using salt to melt ice).
C. Colligative Properties – Properties that depend on
the number of solutes and the nature of the solvent
but NOT on the identity of the solute.
i. Boiling point elevation and freezing point
depression are colligative properties.
ii. The more particles of solute a solution contains,
the more the affect on boiling & melting points.
Number of solute  :
B.P. of Solvent 
: F.P. of Solvent 
Notes
D. Conductivity – conductivity of electrical
current by a solution caused by the presence
of electrolytic solutes.
1. Electrolytes – are solutes that dissociate/ionize
(separate into ions) an aqueous solution and as
a result, the solution is able to conduct
electricity (Ex: salts such as NaCl or CaCl2).
2. Electricity - the flow of charges (such as ions in
solution or electrons in metallic bonds).
3. The higher the concentration of ions within a
solution, the greater the degree of conductivity
of a solution.