Government Property
NOT FOR SALE
Senior High
School
NOT
General Chemistry 2
Quarter 3 - Module 2
Physical Properties of Solution
Department of Education ● Republic of the Philippines
What I Know
Multiple Choice. Encircle the letter of the best answer from
among the given choices.
1. The following are units of concentration, except:
A. Percent by Mass
B. Parts per Million
C. Mole Fraction
D. Mole
2. It is the ratio of the mass of a solute to the mass of the
solution, multiplied by 100 percent.
A. Percent by Volume
B. Percent by Mass
C. Molality
D. Molarity
3. These units of concentration are unitless, except:
A. Mole Fraction
B. Percent by Mass
C. Molarity
D. Percent by Volume
4. What is the unit of molarity?
A. mol/kg
C. mol/L
B. mol
D. none of the above
5. What is the unit of parts per million (ppm)?
A. mg/mol
B. mol/mg
C. mg/L
D. mol/L
6. These properties depend on the collective effect of the
concentration of solute particles present in a solution.
A. Noncolligative Properties B. Colligative Properties
C. Solute Properties
D. Concentration Properties
7. These are colligative properties, except:
A. Vapor Pressure Lowering B. Boiling Point Depression
C. Boiling Point Elevation
D. Freezing Point Depression
8. The Latin word for Colligative, coligare, means:
A. Tied differently
B. Tied together
2
C. Untied differently
D. Untied together
9. What is a nonvolatile solute?
A. Solute that has a vapor pressure of its own
B. Solute that does not have a vapor pressure of its own
C. A & B
D. None of the above
10.
What is an electrolyte?
A. A substance that can conduct electricity when dissolved in
water
B. A substance that does not conduct electricity when
dissolved in water
C. A substance that sometimes conduct electricity when
dissolved in water
D. A substance that can never conduct electricity when
dissolved in water
3
Lesson
1
Concentration Units
What I Need to Know
This module discusses about the properties of solutions,
solubility, and the stoichiometry of reactions in solutions.
After going through this module, you are expected to
1. Use different ways of expressing concentration of
solutions: percent by mass, mole fraction, molarity,
molality, percent by volume, percent by mass, ppm
(STEM_GC11PPIIId-f-111);
2. Perform stoichiometric calculations for reactions in
solution (STEM_GC11PPIIId-f-112);
What’s New
Activity 3.1.1. Find Me! Locate the words
associated with concentration units in the grid. The words
can be running in horizontal, vertical, and diagonal
directions.
1
F
A
H
Y
J
K
F
K
D
K
R
E
Y
O
E
A
M
P
E
R
C
E
N
T
B
Y
M
A
S
S
G
G
O
H
H
J
Y
J
S
N
O
O
S
L
J
S
H
S
L
N
Y
T
F
Q
S
M
L
E
Y
E
O
E
B
G
E
A
I
J
L
O
A
A
R
E
A
L
J
D
I
K
F
H
E
A
L
F
R
R
E
F
U
Y
C
A
S
Q
R
R
F
V
R
I
E
A
A
T
T
V
F
P
O
D
A
E
E
A
T
G
I
I
I
I
A
J
P
G
E
S
C
N
N
Y
B
H
T
O
L
S
L
M
Y
G
F
B
T
C
S
C
F
H
N
A
E
T
D
I
G
H
O
E
I
G
G
W
W
D
L
A
V
S
O
L
U
T
E
S
O
R
K
F
D
O
S
J
D
E
F
A
G
Y
M
K
N
S
F
E
M
U
L
O
V
Y
B
T
N
E
C
R
E
P
S
N
O
I
T
A
R
T
N
E
C
N
O
C
E
1. _____________________
2. _____________________
3. _____________________
4. _____________________
5. _____________________
6. _____________________
7. _____________________
8. _____________________
9. _____________________
10. _____________________
What Is It
In the previous lessons we discover the phase changes in
terms of the accompanying changes in energy and forces
between particles.
Many chemical reactions take place between ions and
molecules dissolved in water or other solvents, rather than
between pure solids, liquids, or gases. Previously, we looked at
the properties of gases, liquids, and solids. In this lesson, we
will examine the properties of solutions, concentrating mainly
2
on the role of intermolecular forces in solubility and other
physical properties of solution.
Quantitative study of a solution requires knowing its
concentration, that is, the amount of solute present in a given
amount of solution. Several different concentration units are
used by chemists, each of which has strengths as well as
drawbacks. Let us examine the units of concentration: percent
by mass, mole fraction, molarity, molality, percent by volume,
and parts per million (ppm).
Types of Concentration Units
1. Percent by Mass
The percent by mass (also called percent by weight
or weight percent) is the ratio of the mass of a solute to
the mass of the solution, multiplied by 100 percent:
Equation (1.1)
The percent by mass is a unitless number because it is a ratio
of two similar quantities.
Example 1.1
A sample of 0.894 grams (g) of potassium chloride (KCl) is
dissolved in 54.8 grams of water. What is the percent by mass
of KCl in the solution?
Strategy
We are given the mass of a solute dissolved in a
certain amount of solvent. Hence, we can calculate the mass
percent of KCl using Equation (1.1).
3
Solution
We write
= 1.61%
2. Mole Fraction (X)
The mole fraction of a component of a solution, say,
component A, is written XA and is defined as
Equation (1.2)
The mole fraction is also unitless, because it too, is a ratio of
two similar quantities.
Example 1.2
What is the mole fraction of the solute in a 40% by mass
ethanol (C2H6O) solution in water?
Strategy We are given the percentage by mass (40%) of the
solute in the solution. Hence, we can calculate the mole fraction
through (1) converting the concentration units based on the
mass or moles of a solute and solvent or mass percentage, it is
useful to assume a certain total mass of solution; (2) changing
the masses of the components ethanol and water to number of
moles; (3) substituting the values obtained in the formula and
solve for the mole fraction of the solute ethanol, and solvent
water.
Solution We write
(1)Assume there is exactly 100 grams of solution. Because
the solution is 40% ethanol (C 2H6O), it contains 40 grams
of ethanol and 60 grams of water.
(2)
4
(3)
The mole fraction of water can be solved using the formula:
3. Molarity (M)
Molarity is defined as the number of moles of solute in 1
L of solution; that is,
Equation (1.3)
Thus, the unit of molarity is mol/L.
Example 1.3
Determine the molarity of the solution with 0.124 mol of CoCl 2 in
0.654 L of solution.
Strategy
We are given the mole of a solute dissolved in a
certain amount of solution. Hence, we can calculate the
molarity of CoCl2 using Equation (1.3).
Solution
We write
4. Molality (m)
Molality is the number of moles of solute dissolved in 1
kg (1000 g) of solvent – that is,
Equation (1.4)
Thus, the unit of molality is mol/kg.
5
Example 1.4
The density of a 2.45 M aqueous solution of methanol (CH3OH)
is 0.976 g/mL. What is the molality of the solution? The molar
mass of methanol is 32.04 g.
Strategy
To calculate the molality of a solution, we need to
know the number of moles of methanol and the mass of solvent
in kilograms. We assume 1 L of solution, so the number of
moles of methanol is 2.45 mol.
Solution Our first step is to calculate the mass of water in 1 L
of the solution, using density as a conversion factor. The total
mass of 1 L of a 2.45 M solution of methanol is
Because this solution contains 2.45 moles of methanol, the
amount of water (solvent) in the solution is
The molality of the solution can be calculated by converting 898
g to 0.898 kg:
5. Percent by Volume
The percent by volume is used to express the
concentration of a solution when the volume of a solute
and the volume of a solution are given, multiplied by 100.
Equation (1.5)
The percent by volume is a unitless number because it is a
ratio of two similar quantities.
Example 1.5
In a solution, there is 122.4 mL solvent and 5.24 mL solute
present. Find the percent by volume.
6
Strategy We are given the volume of a solute dissolved in a
certain amount of solvent. Hence, we can calculate the volume
percent using Equation (1.5).
Solution We write
= 4.11%
6. Parts per million
A concentration of a solution that contained 1 g solute
and 1000000 mL solution (same as 1 mg solute and 1 L
solution) would create a very small percentage
concentration. Because a solution like this would be so
dilute, the density of the solution is well approximated by the
density of the solvent; for water, that is 1g/mL (other
solvents are different case). So, after solving and converting
the mL of solution into grams of solution (assuming that the
solvent is water):
We get (1g solute)/(1000000 g solution). Because both the
solute and the solution are now expresses in terms of grams, it
could now be said that the solute concentration is 1 part per
million (ppm).
The ppm unit can also be used in terms of volume/volume (v/v)
instead.
Example 1.6
A solution has a concentration og 1.24 g/L. What is its
concentration in ppm?
Strategy
We need to convert the mass in grams into
milligrams and then re-write the concentration in mg/L
7
Solution We write
What’s More
Activity 3.1.2. Let’s do this! Answer the following
problems. Write your full solution on your answer sheet
and box the final answer.
1. Hydrogen peroxide, H2O2, is used by some water
treatment systems to remove the disagreeable odor of
sulfides in drinking water. An aqueous solution of H 2O2
prepared in the laboratory was found to have a
concentration of 20.0% by mass. What is the mole fraction
of H2O2?
2. What is the molality of a solution containing 0.75 moles of
sodium hydroxide in 500 mL of water at 25℃? The density
of water at 25℃ is 1 g/mL. (Hint: d=m/v)
3. A sample of 0.938 g of sodium hydroxide (NaOH) is
dissolved in 60.9 g of water. What is the percent by mass
of NaOH in the solution?
What I Have Learned
Activity 3.1.3. Complete me! Complete the table by
giving the equation and the units of concentration
mentioned.
UNITS OF
CONCENTRATION
1. Percent by Mass
2. Molarity
3. Mole Fraction
4. Molality
5.
Percent
by
Volume
6. Parts per Million
EQUATION
8
UNIT
What I Can Do
Activity 3.1.4 Give Example! Give two examples of
the topics listed below that are present in everyday life.
A. Solute
B. Solvent
C. Solution
D. Concentration
9
Lesson
2
Colligative Properties of
Solution
What I Need to Know
This module discusses about the colligative properties of
electrolyte and nonelectrolyte solutions.
After going through this module, you are expected to
1. Describe the effect of concentration on the colligative
properties of solutions (STEM_GC11PPIIId-f-115);
2. Differentiate the colligative properties of nonelectrolyte
solutions and of electrolyte solutions (STEM_GC11PPIIIdf-116).
What’s New
Activity 3.2.1. Match Me! Choose the answer that best
matches each of the definitions below. Write the letter of your
answer on the column entitled “Match”.
Definition
1
2
Match
It is a direct measure
of escaping tendency
of molecules.
It depends on the
collective effect of the
concentration
of
solute
particles
Key Terms
A. Colligative
Properties
B. Boiling Point
Elevation
10
3
4
5
present
in
the
solution.
It
is
used
to
determine
the
reduced
vapor
pressure.
The temperature at
which
the
vapor
pressure is 1 atm will
be higher than the
normal boiling point
by an amount.
It is the difference in
temperature between
the freezing point of a
pure solvent and that
of a solution.
C. Vapor
Pressure
D. Freezing Point
Depression
E. Vapor
Pressure
Lowering
F. Raoult’s Law
What Is It
In the previous lessons we discover that a solution is
described in terms of concentration of one or more solutes
present in it.
There are some important physical properties of solution
which are more directly dependent on the concentration of
solute particles. Previously, we looked at the different
concentration units and how they are utilized to determine the
desired result. In this lesson, we will examine the properties
that are called colligative (Latin, coligare – which means “tied
together”) properties which mean, they depend on the collective
effect of the concentration of solute particles present in the
solution. These properties include: (1) vapor pressure lowering,
(2) boiling point elevation, (3) freezing point depression, and (4)
osmotic pressure.
11
Because of their direct relationship to the number of solute
particles, the colligative properties are very useful for
characterizing the nature of a solute after it is dissolved in a
solvent and for determining the molar masses of substances.
The latter will be discussed in the next lesson.
Effect of solute concentration on the colligative properties
of solutions
The concentration or amount of nonvolatile solute (i.e., a
solute that does not have a vapor pressure of its own) in the
solution influences the colligative properties of solutions. The
result will depend on the ratio between the number of solute
and solvent particles in the solution and not on the solute's
identity. However, it is necessary to consider whether the solute
is an electrolyte or a nonelectrolyte.
Effect of solute concentration on the colligative properties
of solutions
1. Vapor Pressure Lowering
A direct measure of the escaping capacity of molecules is
vapor pressure. A pure liquid (solvent) can achieve equilibrium
with its vapor in a closed container. And the pressure exerted
by the vapor is called vapor pressure until the equilibrium is
attained. A substance that does not have a noticeable vapor
pressure is nonvolatile, whereas one that has a vapor pressure
is volatile.
If a liquid evaporates readily, a significant amount of the
molecules would be present in the gas phase, resulting in a
high vapor pressure. A surface completely filled by liquid
molecules is seen on the left, some of which have evaporated
and formed a vapor. On the right, a nonvolatile solute like salt
or sugar has been dissolved into the solvent, having the effect
of diluting the water. The addition of a non-volatile solute
resulted in lowering of the solvent's vapor pressure. The
lowering in vapor pressure depends on the amount of dissolved
solute particles. The molecular essence of the solute is not
12
taken into consideration since the vapor pressure is simply a
solvent's physical property and does not undergo a chemical
reaction with the solvent and does not escape into the gas
phase by itself.
Figure 1: Volatile Solvent VS Non-volatile Solute
It should be remembered that the decrease in the vapor
pressure of the solution in this case is directly proportional to
the fraction of the volatile molecules in the oil, which is the
solvent’s mole fraction. It is possible to assess this decreased
vapor pressure using Raoult’s Law (1886).
Figure 2: Relationship Between Vapor Pressure and Mole
Fraction of Water
Where:
13
Recall from the definition of mole fraction that in a twocomponent solution (a solvent and a single solute), Xsolvent = 1 –
Xsolute.
While the chemical nature of the solute is not a factor to
consider, it is important to take into consideration whether the
solute is an electrolyte or nonelectrolyte. Ionic compounds such
as sodium chloride, NaCl, are strong electrolytes that dissociate
into ions, resulting in a greater number of dissolved particles
when they dissolve in solution. Consider two distinct equivalent
concentration solutions: one is made of ionic compound NaCl,
and the other is made of molecular compound glucose
(C6H12O6). The equations below show what happens when
these solutions dissolve:
NaCl (s)
 Na+ (aq) + Cl- (aq)
C6H12O6 (s)

C6H12O6 (aq)
particle
2 dissolved particles
1 dissolved
The sodium chloride, NaCl dissociates into 2 ions, while
glucose does not dissociate. Thus, twice as many dissolved
particles as in the case of NaCl would result in equal
concentrations of each solution. In the NaCl solution
(electrolyte), the vapor pressure of the solvent can be reduced
twice as much as that of the solvent in the glucose
(nonelectrolyte) solution. Since the salt solution surface is now
filled with more solvent particles, there is less space for solvent
molecules to evaporate, decreasing the solvent's water vapor
pressure.
2. Boiling Point Elevation
The addition of a non-volatile solute decreases the vapor
pressure of the solution, so that the vapor pressure of the
solution is returned to a value conforming to the pure solvent,
the temperature must be increased. In fact, the temperature at
which the vapor pressure is 1 atm is greater than the normal
boiling point by an amount known as the boiling point elevation.
14
Figure 3 below shows the phase diagram of a solution and
the effect that the lowered vapor pressure has on the boiling
point of the solution compared to the solvent. In this case the
sucrose solution has a higher boiling point than the pure
solvent. Since the vapor of the solution is lower, more heat
must be supplied to the solution to bring its vapor pressure up
to the pressure of the external atmosphere. The boiling point
elevation is the difference in temperature between the boiling
point of the pure solvent and that of the solution.
Figure 3: The Result of Lowering the Vapor Pressure in a
Solution to the Boiling Point
Figure 4: Normal Boiling Point for Water (solvent) as a Function
of Molality in Several Solution Containing Sucrose (a nonvolatile solute)
For dilute solution, the elevation of the boiling point is
directly proportional to the molal concentration of the solute:
The molal boiling point elevation constant Kb, has a
specific value depending on the identity of the solvent.
3. Freezing Point Depression
The freezing point of a substance is the temperature at
which the solid and liquid forms can coexist indefinitely, at
equilibrium. Under these conditions molecules pass between
the 2 phases at equal rates because their escaping tendencies
from the two phases are identical.
Figure 5 below shows the phase diagram for a pure
solvent and how it changes when a solute is added to it. The
solute lowers the vapor pressure of the solvent resulting in a
lower freezing point for the solution compared to the pure
solvent. The freezing point depression is the difference in
temperature between the freezing point of a pure solvent and
that of a solution. On the graph, Tf represents the freezing point
depression.
Figure 5: The Result of Lowering the Vapor Pressure in a
Solution to the Freezing Point
If a substance is applied to a solvent such as water at a
given temperature, the solute-solvent interactions prohibit the
solvent from entering the solid phase, causing the temperature
to drop further until the solution solidifies. As a result, more
energy must be removed from the solution to freeze it and the
freezing point of the solution is power than that of the pure
solvent.
16
The degree of the freezing point depression is directly
proportional to the solution's molality. Thus:
Where:
– is the molal freezing point depression constant, a
constant that is equal to the change in the
freezing point for a 1 molal solution of a
nonvolatile molecular solute
– freezing point depression
– molality of solute
The study of colligative properties of electrolytes requires
a slightly different approach than the one used for the
colligative properties of nonelectrolytes. The explanation is
because electrolytes dissociate in solution into ions, and thus
as they dissolve, one unit of an electrolyte compound splits into
two or more particles. Remember that it is the total number of
solute particles that determines the colligative properties of a
solution.
For example, each unit of NaCl dissociates into two ions –
+
Na and Cl-. The colligative properties of a 0.1 m NaCl solution
should, thus, be twice as high as those of a nonelectrolytecontaining 0.1 m solution, such as sucrose. Similarly, we would
expect a 0.1 m CaCl2 solution to depress the freezing point by
three times as much as a 0.1 m sucrose solution because each
CaCl2 produces three ions. We characterize a quantity called
the Van't Hoff factor to account for this effect, given by
Thus, should be 1 for all nonelectrolytes. For strong
electrolytes such as NaCl and KNO 3, should be 2, and for
strong electrolytes such as Na2SO4 and CaCl2, should be 3.
Consequently, the equations for colligative properties must be
modified as
17
In reality, the colligative properties of electrolyte solutions
are usually smaller than anticipated because at higher
concentrations, electrostatic forces come into play and bring
about the formation of ion pairs. An ion pair is made up of one
or more cations and one or more anions held together by
electrostatic forces. The presence of an ion pair reduces the
number of particles in solution, causing a reduction in the
colligative properties. Electrolytes containing multicharged ions
such as have a greater tendency to form ion pairs than
electrolytes such as NaCl and KNO3, which are made up of
singly charged ions.
Table 1. The van’t Hoff Factor of 0.0500 M Electrolyte
Solution at 25℃
What’s More
Activity 3.2.2. True or False! Write the word True if
the idea expressed in the statement is correct. If the
statement is wrong, write the word False. Underline the
word/s that make the statement wrong, then write the
correct answer.
_______________________1. At a given temperature, if a
substance is added to a solvent like water, the solute-solvent
interactions prevent the solvent from going into the solid phase,
requiring the temperature to decrease further before the
solution will liquify.
18
_______________________2. For dilute solution, the elevation
of the boiling point is reversely proportional to the molal
concentration of the solute.
_______________________3. When a liquid evaporates
easily, it will have a large number of its molecules in the gas
phase resulting to a high vapor pressure.
_______________________4. While the chemical nature of the
solute is not a factor to consider, it is important to take into
consideration whether the solute is an electrolyte or
nonelectrolyte.
_______________________5. The concentration or amount of
nonvolatile solute in the solution does not influence the
colligative properties of solutions.
What I Have Learned
Activity 3.2.3. Give Example! Give two examples of
the topics listed below that happen in everyday life.
1. Vapor Pressure Lowering
2. Boiling Point Elevation
3. Freezing Point Depression
What I Can Do
Activity 3.2.4. Know Me! Answer the following
questions. You may refer to books and the internet to
solidify your explanation.
1. The ice cream made in an old-fashioned way is where the
maker has a tub full of mixed ingredients immersed in a
bigger tub filled with ice and salt. Why do you think is salt
added to the ice?
2. Which would increase more the boiling point of water: salt
or sugar? Why?
19
Summary
The concentration of a solution can be expressed as
percent by mass, mole fraction, molarity, and molality. The
choice of units depends on the circumstances.
Raoult’s Law states that the partial pressure of a
substance A over a solution is equal to the mole fraction (X A) of
A times the vapor pressure (PA°) of pure A. An ideal solution
obeys Raoult’s Law over the entire range of concentration. In
practice, very few solutions exhibit ideal behavior.
The choice of a concentration unit is based on the
purpose of the experiment. For instance, the mole fraction is
not used to express the concentrations of solutions for titrations
and gravimetric analyses, but it is appropriate for calculating
partial pressures of gases and for dealing with vapor pressures
of solutions. The advantage of molarity is that it is generally
easier to measure the volume of a solution, using precisely
calibrated volumetric flasks, than to weigh the solvent. For this
reason, molarity is often preferred over molality. On the other
hand, molality is independent of temperature, because the
concentration is expressed in number of moles of solute and
mass of solvent.
Percent by mass is like molality in that it is independent of
temperature. Furthermore, because it is defined in terms of
ratio of mass of solute to mass of solution, we do not need to
know the molar mass of the solute to calculate the percent by
mass. Sometimes it is desirable to convert one concentration
unit of a solution to another; for example, the same solution
may be employed for different experiments that require different
concentration units for calculations.
Vapor-pressure lowering, boiling-point elevation, freezing
point depression, and osmotic pressure are colligative
properties of solutions; that is, they depend only on the number
of solute particles that are present and not on their nature.
In electrolyte solutions, the interaction between ions leads
to the formation of ion pairs. The Van’t Hoff factor provides a
measure of the extent of dissociation of electrolytes in solution.
20
KEY EQUATIONS
Percent
by Mass
Molarity
Mole
Fraction
Molality
Percent
by
Volume
Parts
per
Million
Vapor
Pressur
e of
Solution
Boiling
Point
Elevatio
n
Freezing
Point
Depressi
on
Van’t
Hoff
Factor
21
Assessment: (Post-Test)
Multiple Choice. Encircle the letter of the best
answer from among the given choices.
1. The unit of molality is?
A. mol/kg
B. mol/L
C. unitless
D. L/mol
2. The mass of solution is equal to:
A. Sum of moles of all components B.
solute + volume of solvent
C. Mass of solute + mass of solvent
above
Volume
of
D. All of the
3. Why are some units of concentration unitless?
A. Just because
B. Because it is a ratio of two similar quantities
C. Because it is a ratio of two different quantities
D. Because it is not a ratio of two similar quantities.
4. It is used to express the concentration of a solution when
the volume of a solute and the volume of a solution are
given, multiplied by 100.
A. Percent by Mass
B. Molality
C. Molarity
D. Percent by Volume
5. What is the often-preferred unit of concentration for
calculating partial pressures of gases and for dealing with
vapor pressures of solutions?
A. Molarity
B. Molality
C. Mole Fraction
D. Parts per million
6. Why are colligative properties very useful for
characterizing the nature of solute after it is dissolved in a
solvent?
A. Because of their indirect relationship to the
number of solute particles
22
B. Because of their direct relationship to the number
of solute particles
C. Because of their reverse relationship to the
number of solute particles
D. Because of their indirect relationship to the
number of solute particles
7. What will establish equilibrium with its vapor in a closed
container?
A. Pure Solid
B. Pure Gas
C. Pure Liquid
D. None of the above
8. Why is the chemical nature of the solute not considered in
the lowering of the vapor pressure?
A. Because it depends on the number of the solute
particles that have been dissolved
B. Because vapor pressure is merely a physical
property of the solvent and does not undergo a
chemical reaction with the solvent and does not itself
escape into the gas phase
C. A & B
D. None of the above
9. If the vapor of the solution is lower, what must be supplied
to the solution to bring its vapor pressure up to the
pressure of the external atmosphere?
A. Less heat
B. More heat
C. No heat shall be supplied D. None of the above
10.
In Freezing Point Depression, under what conditions
molecules pass between the 2 phases at equal rates
because their escaping tendencies from the two phases
are identical?
A. Equilibrium
B. Non-equilibrium
C. Freezing Point
D. Elevation
23
Key to Answers
ASSESSMENT (PRE-TEST)
1. D
2. B
3. C
6. B
7. B
8. B
What’s New: Activity 3.1.1. Find me!
F
A
H
Y
J
K
F
K
D
K
R
E
Y
O
E
A
M
P
E
R
C
E
N
T
B
Y
M
A
S
S
G
G
O
H
H
J
Y
J
S
N
O
O
S
L
J
S
H
S
L
N
Y
T
F
Q
S
M
L
E
Y
E
O
E
B
G
E
A
I
J
L
O
A
A
R
E
A
L
J
D
I
K
F
H
E
A
L
F
R
R
E
F
1. Percent by Mass
2. Percent by Volume
3. Molality
4. Molarity
5. Mole Fraction
U
Y
C
A
S
Q
R
R
F
V
R
I
E
A
A
T
T
V
F
P
O
D
A
E
E
A
T
G
I
I
I
I
A
J
P
G
E
S
C
N
N
Y
B
H
T
O
L
S
L
M
Y
G
F
B
T
C
S
C
F
H
4. D
9. B
N
A
E
T
D
I
G
H
O
E
I
G
G
W
W
D
L
A
V
S
O
L
U
T
E
S
O
R
K
F
D
O
S
J
D
E
F
A
G
Y
M
K
N
S
F
5. C
10. A
E
M
U
L
O
V
Y
B
T
N
E
C
R
E
P
S
N
O
I
T
A
R
T
N
E
C
N
O
C
E
6. PPM
7. Solute
8. Solvent
9. Solution
10.Concentration
What’s More: Activity 3.1.2. Let’s do This!
1. 0.117
2. 1.5 mol/kg
3. 1.52%
What Have I Learned: Activity 3.1.3. Complete Me!
UNITS OF
CONCENTRATION
1. Percent by Mass
2. Molarity
3. Mole Fraction
4. Molality
5.
Percent
by
Volume
6. Parts per Million
What I Can do: Activity 3.1.4: Give Example!
1. Salt/Sugar
2. Water/Milk/Ethanol
3. Vinegar/Bleach/Steel
4. Hand soap/Soft Drinks/Liquid Medicine
EQUATION
UNIT
unitles
s
mol/L
unitles
s
mol/kg
unitles
s
mg/L
What’s New: Activity 3.2.1.Match me!
1. C
2. A
3. F
4. B
5. D
What’s More: Activity 3.2.2. True or False!
1. Solidify (underline liquify) 2. Directly (underline reversely)
3. T
4. T
5. Influences (underline does not influence)
What Have I Learned: Activity 3.2.3. Give Example!
1. Freeze-Drying/Calibrating PH meters using Sodium Chlorate and Sodium Nitrate
2. Adding a pinch of salt to water when cooking/Sugar Refining
3. Salting an Icy Road/Antifreeze in the Radiator/Ice Cream using ice cream salt
What I Can do: Activity 3.2.4: Know Me!
1. The salt is added because it lowers the freezing temperature of the ice and makes the ice
cream colder faster. The salt added to the ice or water slush is a solute that has affected the
property of the solution it was added to. This property is a colligative property of solution.
2. Salt will increase more the boiling point of water. The increase in boiling point depends
on the number of molecules added to water. Salt is a very small molecule. In addition, it
splits into two particles when in water, the Na + ion and the Cl- ion. In numbers: if suppose
you add 6g of salt into water you add about 4,400,000,000,000,000,000,000 (4.4 * 10 22)
particles to the water. On the other hand, sugar has a molecular weight that is 3 times
larger than that of salt. It does not split up in different particles when in water. So, adding
6 g sugar into water you add around 700,000,000,000,000,000,000 particles (7.3 * 10 21) to
the water. Still a huge number, but considerably less than with salt. To get the same effect
with sugar that you get with salt, you will have to use about 6 times as much sugar as salt.
The same is true in principle with lowering the freezing point of liquids. That is the reason
why we use salt in winter on our streets and not sugar - as we would need 6 times as much
for the same effect. But it will work with sugar too if we use just enough of it.
ASSESSMENT (POST-TEST)
1. A
2. B
3. B
6. B
7. C
8. C
4. D
9. B
25
5. C
10. A
26