08/03/2015
State of matter
General Chemistry , ed. Saunders
1
2
Six changes of states that matter can undergo
and tell you if heat is added or removed for the
change to take place.
Change
Physical state of matter
3
From
To
Heat
Examples
added =
endothermic
Moth crystals disappear
when left in a closet for
several days
Sublimation
solid
gas or
vapour
Resublimation
gas or
vapour
solid
removed
= exothermic
frost forms on a car's
windshield
Evaporation or
vapourization
liquid
gas
added =
endothermic
Rain dries up when the sun
comes out
Melting or
Liquefaction
solid
liquid
added =
endothermic
An ice cube turns into water
when left out of the freezer
Freezing or
Solidification
liquid
solid
removed
= exothermic
A bottle of water will turn
into ice if left in the freezer
Condensation
gas or
vapour
liquid
removed
= exothermic
Drops of water form on the
mirror when taking a hot
shower
http://www.clickandlearn.org/gr9_sci/particle_theory.htm
4
1
08/03/2015
Properties of states
PROPERTY
SOLID
shape
fixed
volume
definite
ability to flow
LIQUID
same as
container
(indefinite)
definite
Quizzes
GAS
• 1. When a solid changes to a liquid it
is called what?
• 2. When a gas reaches its
condensation point it becomes a
what?
• 3. What is it called when a solid
changes directly into a gas?
same as
container
(indefinite)
fills entire
container
(indefinite)
no
yes
yes
can be
compressed
very slightly
very slightly
yes
volume change
with heating
very small
small
large
5
6
Gaseous state of matter
Quiz
How many states of matter are there?
(Scientists call plasmas a state of
matter, too. You do not have to
count plasma as a state of matter for
this question).
a.) two
b.) three
c.) five
8
The forces of attraction that hold molecules
together in a gas state are very weak and that
the spaces between them are much larger
than the spaces between solid and liquid
particles.
Particles of gases can move from place to place
within a container bumping against the walls of
the container and against other particles.
11
2
08/03/2015
Gases :
Energy of gaseous particles:
1. can be compressed into smaller volumes
• rotational,
(their densities can be increased by
• translational
applying increased pressure);
• vibrational
2. exert pressure on their surroundings
This explains why the gas molecules can escape
from a container very easily and they can put
(pressure must be exerted to confine gases)
3. expand without limits (gas samples
pressure on the side of the container (example a
completely and uniformly occupy the
balloon or a tire).
volume of any container)
12
13
4. diffuse into one another (so samples of gas
placed in the same container mix completely,
different gases in a mixture do not separate on
standing).
5. terms of temperature, pressure, the volume
occupied, and the number of molecules present
describe the amounts and properties of gases.
(a) Diffusion (b) Effusion
15
3
08/03/2015
Pressure, P.
Graham found that the effusion rate of a gas was inversely
proportional to the square root of the density (d)
This is known as Graham’s law
1
d
effusion rate 
Pressure = Force / area;
(constant P and T )
P
effusion rate ( A)
dB
MB


effusion rate ( B)
dA
MA
SI unit Pascal, Pa ;
Where Mi is the molar mass of species i
1 Pa 
F
area
1N
1kg

2
1m
1 m 1 s2
16
17
Pressure units
5
6
≡ 10 dyn/cm
5
1 at
0.980665 ×10
1 atm
1.01325 ×10
1 Torr
133.322
1 psi
6.895×10
5
2
1.0197
0.980665
≡ 1 kp/cm
1.01325
1.0332
−3
1.3595×10
−3
70.307×10
1.3332×10
3
atm
−5
1.0197×10
68.948×10
2
Torr
−6
9.8692×10
pound
per
square
inch )
10
at
−5
10
torr
1 bar
bar
2
standard
atmosph
ere
≡ 1 N/m
technical
atmosph
ere
bar
pascal
Pa
1 Pa
psi
−3
7.5006×10
−6
145.04×10
0.98692
750.06
14.5037744
0.96784
735.56
14.223
≡ p0
760
−3
1.3158×10
−3
68.046×10
Atmospheric pressure is
measured with a
barometer. A Torricelli
barometer consists of a
glass tube sealed at one
end, about 80 cm in
length.
14.696
−3
= 1 mmHg
19.337×10
−3
51.715
≡ 1 lbF/in
−3
18
2
19
4
08/03/2015
Laws for gaseous state of matter
• A manometer is used to measure
the pressure inside closed
containers
Boyle’s law
-Volume of gas sample varies inversely with
pressure at constant temperature
Charle’s law
-Volume of a gas sample varies directly with Kelvin
temperature at constant pressure
Combined law
Pi Vi Pf V f

Ti
Tf
Open-end manometer. (a) The pressure of the trapped gas, P gas
equals the atmospheric pressure, Patm. Trapped gas pressure (b)
higher and (c) lower than atmospheric pressure.
20
Example 1:
22
Dalton’s law of Partial Pressures
A sample of gas has a volume of 283 mL at 25oC and 0.500 atm
pressure. What is the volume at 100oC and 1 .00 atm?
Ti = 25o C = 273+ 25= 298 K
Vi = 283 mL
Pi = 0.500 atm
Tf = 100oC = 273 + 100 = 373 K
Vf = ?
PTOTAL= Pgas A + Pgas B + Pgas C +….+ Pgas Z
Pf = 1.00 atm
Vf =
Pi Vi T f

Ti
Pf
Vf 
This law assumes that each gas in the mixture
is behaving like an ideal gas.
(0.500 atm  283 mL)
373K

 177 mL
298K
1.00 atm
23
General chemistry, 7-th ed.
26
5
08/03/2015
Ideal gas law
Example 1: The vapour pressure of water in
25OC is 3.17 kPA. The pressure of hydrogen in
PV = nRT or
the same temperature is 99.2 kPa. What is the
pressure of mixture of hydrogen in water?
PV
R
nT
PTotal = Pwater + PHydrogen =
= 3.17 kPa + 99.2 kPa= 102.4 kPa
Where: P- pressure, V- volume; n-number of
moles, R-gas constant (0.08206
27
L atm
K mol
)
30
Example 1: What is the pressure of 1.00 mole of
gas that has a volume of 10.0 L at 100.0oC?
P= ?
• Example 2: A helium gas cylinder
used to fill baloons has a volume of
180 L and a pressure of 150 atm at
25OC. How many moles of helium are
in the tank?
V= 10.0 L
n = 1.00 mole
L atm
R= 0.08206 K mol
T = 100oC = 100+ 273.2+ 373.2 K
n RT
P

V
L atm
 373.2 K
K mol
 3.06 atm
10 L
1.00 mol  0.08206
31
32
6
08/03/2015
Dalton’s law of Partial Pressures part.2
Self-checking quiz
Ptotal V = ntotal R T
• Nitrogen gas is housed in a sealed,
hollow cylinder at a pressure of 105
Pa. Its temperature is 300K and its
volume is 30 dm3. The volume within
the cylinder is increased to 45dm3
and the temperature is increased at
the same time to 310 K. What is the
new pressure?
ntotal = nA + nB + nC; where
n is number of moles of each kind gasses
Ptotal 
Ptotal
PA 
ntotal R T (n A  n B  nC  ...) RT

V
V
n A RT nB RT nC RT



 .......
V
V
V
n A RT
V
PB 
n B RT
V
PC 
nc RT
V
35
Mole fraction, XA
XA 
Example 1: The mole fraction of oxygen in
the atmosphere is 0.2094. Calculate the
partial pressure of O2 in air when the
atmospheric pressure is 760 torr.
nA
numbers of A mole

total numbers of moles of all compounds n A  n B  nC  ...
XA 
PA
Ptotal
XB 
PB
Ptotal
XC 
36
PC
Ptotal
Ptotal = XAPA + XBPB+ XC PC + ……
37
38
7
08/03/2015
Quiz
• PO2 = Xo2 x Ptotal = 0.2054 x 760 torr
= 159 torr
What is the total pressure of the mixture containing
nitrogen (PN2 = 3.00 atm; XN2 = 0.27) and helium
( PHe = 6.00 atm, XHe = 0.73)
a) 9 atm; b)6 atm; c) 3.81; d) 5.19 atm
39
40
Real gas
Self-checking quiz
PV = nRT; assuming that n = 1,
• A mixture containing oxygen and
nitrogen gas has a total pressure of
0.67 atm, the partial mixture of
nitrogen is 0.33 atm. Determine the
percentage of oxygen and nitrogen
gas in the mixture.
41
PV
 1.0
RT
42
8
08/03/2015
(a) In an ideal gas, molecules would travel in straight lines. (b)
In a real gas, the paths would curve due to the attractions
between molecules.
Fig. Deviation of the ideal gases behaviour
http://www.chem.ufl.edu/~itl/4411/lectures/lec_e.html
45
46
Van der Waals equation:
(P 
n2 a
) (V  n b)  nRT
V2
Substance
Helium, He
Neon, Ne
Hydrogen, H 2
P –pressure
V- volume
n- number of moles
a
L2 atm mol  2
0.03421
0.2107
0.02444
b
L mol 1
0.02370
0.01709
0.02661
R- gas constant
Ammonia, NH 3
4.170
0.03707
T – temperature (K)
Water, H 2 O
5.464
0.03049
a,b- constants;
a- correction for molecular attraction
b- correction for volume of molecules
47
48
9
08/03/2015
http://www.hotwatt.com/table3.htm
Viscosity
The property of liquid which is a measure of flow resistance. It
is related to the strength of the forces acting between
Comparison of some physical properties of liquids and gases
Compound
Density
(at or near room temp.
and
atmospheric pressures)
(lb/cu.ft.)
Specific Heat
(BTU/lb/°F)
Ethanol
49.6
0.60
Gasoline
48.6
0.675
substance molecules.
It could be hydrogen bonding (water) or dispersion forces
(mercury).
The stronger the intermolecular forces of attraction the more
viscous the liquid is. Substance which has a great ability to form
Milk
64,5
~1.00
Vegetable oil
57.5
0.43
hydrogen bonds shows higher viscosity in comparison with
Water
62.3
1.00
substances forming dispersion bonds.
Air (80OF)
0.073
0.240
Carbon dioxide
0.113
0.199
Oxygen
0.082
0.218
Water vapour (steam;
212oF)
0.037
0.482
substance
1.00
diethyl ether
(CH3-CH2)2O
0.23
benzene C6H6
0.65
glycerin
C3H2(OH)3
280
mercury
1.5
motor oil,
SAE30
200
honey
~10,000
molasses
~5000
pancake syrup
~3000
T/°C
51
Surface tension
viscosity
water H(OH)
viscosity/cP
50
Specific viscosity (i.e., relative to
water) of some liquids at 20°C.
Adhesion forces- the strength
which clings dissimilar particles
and/ or surface to one another.
Cohesion forces- the strength
which clings similar or identical
particles or surfaces to one
another.
0
10
20
40
1.8
1.3
1.0
0.65 0.47 0.36 0.28
60
80
100
Viscosity of Water as a Function of Temperature
http://www.chem1.com/acad/webtext/states/liquids.html
53
54
10
08/03/2015

F
d
A rectangular wire frame of height d
with a sliding bar. A film of soap with
Surface tension (σ) is the ratio between force (F) and the
surface tension σ fill the space made
length (d) along which force acts.
by the frame and the bar.
Example: If the size of the force is F= 4x10-3N and the length
However, there are two surfaces
of the line is d = 5x10-2m, what is the surface tension of the
(bottom and top) of the film so the
liquid?

force acts on a line of length 2d.
F 4 x10 3 N

 0.08 N  m 1 
d 5 x10  2 m
F   2d
55
surface
tension
substance
Example 1: If the surface tension of a soap film is
σ = 2.5 x10-2 N m-1, the width of the frame is
d = 10x10-2 m and a sliding bar had moved distance
Δ t= 2x10-2 m what a work has done.
Work = force x distance moved;
W= F x Δt
F = σ x 2d;
so W= σ x2d x Δt
W= 2.5x10-2 N m-1 x 2 x 10x10-2 m x 2 x10-2m
56
http://www.insula.com.au/physics/1279/L8.html
water H(OH)
72.7 dyne/cm
diethyl ether (CH3CH2)2O
17.0
0
75.9
benzene C6H6
40.0
20
72.7
glycerin C3H2(OH)3
63
50
67.9
mercury (15°C)
487
100
58.9
n-octane
21.8
sodium chloride
solution (6M in water)
82.5
sucrose solution
(85% in water)
76.4
sodium oleate (soap)
solution in water
25
°C
dynes/cm
Surface tension of water
Water surface tension
vs. temperature
= 1 x10-4N m = 1 x10-4 J
Surface tension of some liquids
Unit of surface tension [N m-1 or J m-2]
57
58
11
08/03/2015
Some effects connected with surface tension
Wine tears
Natural waterproof
surface
h = elevation of the liquid (m)
γ = surface tension (N/m)
θ = contact angle (radians)
ρ = density of liquid (kg/m3)
g = acceleration of gravity (m/s–2)
r = radius of tube (m)
Meniscuses
http://www.chem1.com/acad/webtext/states/liquids.html
59
http://www.chem1.com/acad/webtext/states/liquids.html
60
Example: What is the surface tension of liquid which filled the
capillary if the height of the liquid in capillary was 20 mm,
the density of liquid was 150 kg/m 3, the radius of capillary was
6 x 10-3m. Assume that the cos θ =1.0


h gr
2 cos 
(2 x102 m)(150 kg m 3 )(9.81m s 2 )(6 x 103 m)
 0.08829 kg s 2  0.08829N m 1
2 x1
σ = 88.29 mN m-1
61
http://www.chem1.com/acad/webtext/states/liquids.html
62
12
08/03/2015
Evaporation, vaporization
evaporation
Liquid
condenstation
Gas
Evaporation or vaporization- escape of molecules from the liquid
state to the gas or vapour state.
Process of molecules evaporation causes
cooling the surface.
E.g. volatile liquids are sprayed on the skin
they evaporate rapidly, cooling the area by
removing heat.
Molecules which energy is greater than average kinetic energy can
overcome the attractive forces and break away from the surface of
liquid to become a gas.
63
Vapour pressure – the pressure exerted by a vapour in
equilibrium with its liquid at given temperature.
Because the rate of evaporation increases with increasing
temperature, vapour pressures of liquids always enhance
as temperature increases
65
Easily vaporized liquids are called volatile liquids, and
they have relatively high vapor pressures
Vapor Pressures (in torr) of Some Liquids
0°C
25°C
50°C
75°C
100°C 125°C
water
4.6
23.8
92.5
300
760
benzene
27.1
94.4
271
644
1360
methyl
alcohol
29.7
122
404
1126
diethyl
ether
185
470
1325
2680
1741
4859
66
Plots of the vapor pressures of the liquids in Table above. The normal
boiling point of a liquid is the temperature at which its vapor pressure
is equal to one atmosphere. Normal boiling points are: water, 100°C;
benzene; 80.1°C; methyl alcohol, 65.0°C; and diethyl ether, 34.6°C.
The increase in vapor pressure is not linear with temperature.
67
13
08/03/2015
Distillation, boiling point
The molar heat (or enthalpy) of vaporization (Hvap) of a liquid
The boiling point of a liquid can be defined
as the temperature at which the vapor
pressure of the liquid is equal to the
prevailing atmospheric pressure
is the amount of heat that must be added to one mole of the liquid
at its boiling point to convert it to vapor with no change in
temperature. Heats of vaporization can also be expressed as
energy per gram.
The normal boiling point is the
temperature at which the vapor
pressure is 1 atm
Molecules with higher intermolecular
forces have higher boiling points
A laboratory setup for distillation.
Different liquids have different cohesive forces, so they have different
vapor pressures and boil at different temperatures. A mixture of
liquids with sufficiently different boiling points can often be separated
into its components by distillation. In this process the mixture is
heated slowly until the temperature reaches the point at which the
most volatile liquid boils off.
68
Heats of Vaporization, Boiling Points,
and Vapor Pressures of Some Common Liquids
69
When the temperature of a liquid is changed
from T1 to T2, the vapor pressure of the
Liquid
Vapour
pressure
(Torr at 20oC)
Boiling
point
(at 1 atm,
oC)
Heat of
vapourization at
boiling point
[kJ/mol]
liquid changes from P1 to P2.
These changes are related to the molar heat
of vaporization, Hvap, for the liquid by the
water
17.5
100.0
40.7
Ethyl alcohol
43.9
78.3
39.3
Benzene
74.6
80.1
30.8
Dietyl ether
442.0
34.6
26.0
Carbon tetrachloride
85.6
76.8
32.8
Ethylene glycol
0.1
197.3
58.9
Clausius–Clapeyron equation.
 P   H vap 1 1
ln 2  
(  )
R
T1 T2
 P1 
71
14
08/03/2015
Example: The normal boiling point of ethanol, C 2H5OH, is
78.3°C, and its molar heat of vaporization is 39.3 kJ/mol.
What would be the vapor pressure, in torr, of ethanol at
50.0°C?
General Effects of Intermolecular Attractions on
Physical Properties of Liquids
P1 760 torr at T1 78.3°C + 273.2 = 351.5 K
P2 _?_
at T2 50.0°C + 273.2= 323.2 K
Hvap 39.3 kJ/mol or 3.93 104 J/mol
 P2  3.93x10 4 J mol 1
 
( 1  1 )    1.18
ln 
1
1
 760 torr  (8.314 J mol K ) 351.5K 323.2 K
 P2 

  e 1.18  0.307
 760torr 
P2  0.307  760torr  233 torr
73
As the temperature increases,
the solubility of a gas decrease.
More gas is present in a
solution with a lower
temperature compared to a
solution with a higher
temperature.
Solubility of gas in liquid
Parameters which influence solubility:
a) Temperature
b) Pressure
76
http://www.anton-paar.com/pl-pl/produkty/grupa/pomiartlenu-i-co2/
77
15
08/03/2015
Henry’s Law
The solubility of a gas in a liquid
is directly proportional to the
Cgas = kH Pgas
pressure of that gas above
the surface of the solution.
The Henry's law constant "k" is different for every gas,
temperature and solvent.
The units on "k" depend on the units used for concentration
and pressure. The value for k is the same for the same temperature,
gas and solvent.
This means the concentration to pressure ratio is
the same when pressures change.
78
Example: What is the predicted concentration of
dissolved oxygen, if the partial pressure for oxygen is 56
mm Hg? The concentration of dissolved oxygen is 0.44 g /
100 ml solution. The partial pressure of oxygen is 150 mm
Hg.
79
Self-checking quiz
The Henry’s law constant (kH) for O2
in water at 20oC is 1.28 x10-3 mol/L atm.
At this temperature, how many grams
of O2 will dissolve in 3.00Lof water that
are in contact with pure oxygen of 1
atm?
C2 = 0.15 g O2 / 100 ml solution
Online Introductory Chemistry
81
16
08/03/2015
Solution- system in which one or more substances are
Properties of solution
homogenously mixed or dissolved in another substance.
A simple solution consists from solute and solvent.
Common types of solutions
• Two or more components, homogenous, variable
Phase of
solution
solute
solvent
example
composition
Gas
Gas
Gas
Air
•Dissolved solute migt be molecular or ionic in size
Liquid
Gas
Liquid
Soft drinks
Liquid
Liquid
Liquid
Antifreeze
Liquid
Solid
Liquid
Salt water
Solid
Gas
Solid
H2 in Pt
Solid
solid
solid
brass
•Colored or colorless, usually transparent
•Solute uniformly distributed throughout the
solution
• Physical methods allow to obtain pure solutes
82
83
• Benzene and water are said to be immiscible
• The attractive forces between solute and
solvent hold the solution together.
• The strength of the intermolecular attractive
forces depends on both the solute and
solvent.
• Ethanol and water can be mixed in any
proportion
• These compounds are said to be miscible
• When the strengths of the intermolecular
attractions are similar in solute and solvent,
solutions form.
• Both ethanol and water are polar molecules
that form hydrogen bonds. Solvent and solute
are “similar” and a solution will form.
• Benzene is virtually insoluble in water
• Benzene is nonpolar and very different from
water. Solvent and solute are very “different”
and no solution forms.
84
85
17
08/03/2015
This can be summarized as the rule of thumb “like
dissolves like”.
The basic principles remain the same when the
solutes are solids. Sodium chloride dissolves when
it is added to water.
The sodium and chloride ions are hydrated or
Before the solution forms,
water molecules are only
attracted to other water
molecules and the ions in
NaCl are attracted only to
other ions in the solid. In the
solution, the ions have water
molecules to replace their
oppositely charged
counterparts. In addition,
water molecules are more
strongly attracted to ions
than other water molecules
surrounded by water molecules.
The general term for surrounding a solute particle
by solvent molecules is solvation.
86
Hydration energy (also hydration enthalpy)
is a term for energy released upon attachment of
water molecules to ions. It is a special case of
dissolution energy, with the solvent being water.
87
• Consider the formation of aqueous potassium
iodide
The lattice energy of KI is 632 kJ mol –1
The hydrations energy of KI is –619 kJ mol–1
Total: +13 kJ mol–1
(the value from experiment is +20.33 kJ mol–1)
• The formation of this solution of aqueous
potassium iodide is endothermic
Lattice energy – property of ionic solid which
measure the energy (strength)of bonds in that
ionic compound. Lattice energy may also be
defined as the energy required to completely
separate one mole of a solid ionic compound into
gaseous ionic constituents.
88
91
18
08/03/2015
Colligative properties of solutions
• Consider the formation of aqueous sodium
bromide
These properties depend on the
The lattice energy of NaBr is +728 kJ mol-1
The hydration energy of NaBr is –741 kJ mol-1
Total: -13 kJ mol-1
(the value from experiment is –0.602 kJ mol-1
concentration of solute particles
but NOT on their identity.
Colligative properties depend on
the lowering of the escaping
tendency of solvent particles by
• The formation of this aqueous solution of
sodium bromide is exothermic
the addition of solute particles.
Colligative effects include:
• vapor pressure lowering
• boiling-point elevation
• freezing-point depression
• osmotic pressure
92
http://www.ausetute.com.au/colligative.html
93
Δtf = mKf
Δtb= mKb
Δtf – freezing point depression, oC
Δtb – boiling point elevation; oC
Kf – freezing point depression constant;
oC kg solvent/mol solute
Kb – boiling point elevation constant,
oC
kg solvent/mol solute
m – molality
94
95
19
08/03/2015
Example:
A sample of 1.20 g of a non-volatile organic compound
is dissolved in 60.0 g benzene. The BP of solution is 80.96°C.
BP of pure benzene is 80.08°C. What is the molar mass of the solute.
ΔT = 80.96 - 80.08 = 0.88°C
we only have 60.0 g benzene, not 1000 g.
so # moles solute = molality × #kg solvent
Freezing Point Depression Constants
Compound
Freezing
Point
(oC)
Kf
(oC/m)
water
0
1.853
acetic acid
16.66
3.90
benzene
5.53
5.12
p-xylene
13.26
4.3
naphthalene
80.29
6.94
cyclohexane
6.54
20.0
Carbon
tetrachlori
de
-22.95
29.8
camphor
178.75
37.7
96
97
Osmosis, osmotic pressure
The process of diffusion of solvent molecules (water) from diluted
solution to the concentrated solution through the semipermeable
membrane is called
104
osmosis.
105
20
08/03/2015
Example: What is the osmotic pressure of sucrose solution which
Osmotic pressure
contains 50 g of sucrose (0.146 moles) in 117 g of water. The
density of solution is 1.34 g mL-1. The measurement is at
temperature 25oC.
(π) is a pressure difference
T = 273K + 25 = 298K
between the system and atmospheric pressure. It
R= 0.0821 L atm mol-1 K
could be measured by applying enough pressure to
stop the flow of water due to osmosis in the system.
n RT

V
For concentrated solution
 M RT
-1
1 mL
 125 mL  0.125 L
1.34 g
0.146 moles
M 
 1.17 mol L1
0.125 L
L atm
  1.17 mol L1  0.0821
 298 K  28.58 atm
mol K
V  167 g
n- number of solute moles
T –temperature
V – volume
R – gas constant
M- molarity
For diluted solution
 m RT
m - molality
http://mcatdaily.blogspot.com/2010/05/difference-betweenhypertonic-hypotonic.html
106
107
109
110
21
08/03/2015
http://puretecwater.com/what-is-reverse-osmosis.html
112
111
Approximate Sizes of Dispersed Particles
113
Mixture
Example
Approximate
particle size
suspension
Sand in water
larger than
10,000 Å
Colloidal
dispersion
Starch in
water
10–10,000 Å
solution
Sugar in
water
1–10 Å
114
22
08/03/2015
Colloids
Colloid types
A colloid is a dispersion containing particles
between 1 nm and 1000 nm. Colloid particles are
Dispersed
phase
(solute-like)
Dispersing
medium
(solvent-like)
Common name
Examples
solid
solid
solid sol
Alloys (steel)
Certain gems
(rubies)
liquid
solid
solid emulsion
Cheese, butter,
opals
gas
solid
solid foam
Pumice, styrofoam
usually aggregates of ions or molecules. Colloids
can be made from almost any combination of
gas, liquid, and solid. The particles of which the
colloid is made are called the dispersed material
115
solid
liquid
sols and gels
Milk of magnesia,
mud,
liquid
liquid
emulsion
Milk, mayonnaise,
gas
liquid
foam
Whipped cream,
shaving cream,
foam on beer
solid
gas
solid aerosol
Smoke, dust in air
liquid
gas
liquid aerosol
Fog, mist, clouds116
B. Optical properties
Properties of colloid:
A. Mechanical
1. Brownian movement. Brownian movement is the random
zigzag motion of particles that can be seen under a microscope.
The motion is caused by the collision of molecules with colloid
particles in the dispersing medium.
The Tyndal effect
True solutions involve particle too
2. Diffusion. The sol particles diffuse from higher concentration to
lower concentration region.
However, due to bigger size, they diffuse at a lesser speed.
3. Sedimentation. The colloidal particles settle down under the
influence of gravity at a very slow rate. This phenomenon is
small to scatter light.
Colloidial particles are
large enough to scatter
visible light.
used for determining the molecular mass of the
macromolecules.
117
Light shining through a solution of sodium hydroxide (righ)
and a colloidal mixture. (Photo Researchers, Inc.
http://www.scienceclarified.com/Ci-Co/Colloid.html
119
23
08/03/2015
C. Electrical properties
1. Electrophoresis
2. Electrical double layer
3. Electro-osmosis
120
121
Double electric layer and electroosmotic flow
1. Electrophoresis
Double electric layer originate
Electroosmotic flow
Solution interior
Neutral
Diffusion part of solution
Positive charge
Electrophoretic movement of solutes of various charges
Adsorption part of solution
Ionized surface of silica gel
(solid)
Negative charge
122
123
24
08/03/2015
Originate of electroosmotic flow
+
+
-
-
b
a
anode
cathode
+
-
c
124
125
Wells
Positive
Electrode
(red)
Gel
Box
Gel
http://www.uwplatt.edu/~sundin/363-7/image/l637-32h.gif
126
tutorial_dna_fingerprinting_and_electrophoresis
127
25
08/03/2015
Relative huge surface areas of colloid partices
Adsorption
Electrophoretic mobility of DNA restriction fragments in an agarose
gel. The DNA is from bacteriophage lambda digested with the
restriction enzyme Hind III. The graph shows migration distance in
centimeters by size of the restriction fragment in base pairs.
http://cdn.idtdna.com/Support/Technical/TechnicalBulletinPDF/Gel_Electrophoresis.pdf
128
(water-hating) e.g. milk;
mayonnaise.
This colloid type cannot exist in
polar solvents without the presence
of emulsifying agents.
129
Hydrophilic colloids:
Colloids
Hydrophobic
Stabilization of a colloid (Fe2O3 sol) by electrostatic forces.
1. neutral or slight negative charge on the surface
2. dispersion of the molecules is stabilized by hydration
forces
Hydrophilic
3. thermodynamically stable particles
(water-loving).e.g proteins,
gelatin, jellies
4. reversible
5. there is an affinity between dispersion phase and
dispersion medium
Hydrophobic colloids:
1. negatively charged surface (physical/chemical origin)
2. dispersion of molecules is stabilized by electrostatic repulsion
3. thermodynamically unstable
Hydrophilic groups on the
macromolecule surface help to
keep the macromolecule
suspended in water.
130
4. irreversible (enough time allows the slowly particles
aggregation)
5. there is no affinity between dispersion phase and dispersion
medium, we cannot prepare sol by simple mixing
http://ceeserver.cee.cornell.edu/jjb2/cee6560/7-Coagulation
131
26
08/03/2015
Colloids in life
Medicine - Colloidal medicines being
finely divided, are more effective and
are easily absorbed in our system.
• Antibiotics such as penicillin and
streptomycin are produced in
colloidal form suitable for injections.
• Halibut-liver oil and cod-liver oil
• Food – milk (emulsion of butterfat in
water protected by a protein, casein);
• Salad dressing,
• gelatin deserts,
• fruit jellies
• whipped cream
• Ice cream is a dispersion of ice in cream.
• Bread is a dispersion of air in baked
dough.
132
Quiz
133
Quiz
• Which statement is not true.
a) particles in a colloid will reflect light
b) the particles of a solution are
molecule in size
c) a suspension can be filtered
d) a solution can be filtered
134
• Classify the following solutes as:
suspension, colloid, solution
A) smoke; B) orange juice;
C) whipped cream; D)marshmallow
E) 3% dihydrogen dioxide
135
27
08/03/2015
Emulsifying agents are added components that
In water, soap and detergents form
stabilize emulsions.
micelles where the hydrophobic
hydrocarbon tail is orientated towards
The “like dissolves like” rule helps explain how
the center and the hydrophilic head
soaps and detergents work.
is pointed out of the micelle. Oil and
grease collect near the center of the
Oily and greasy material is the “glue” that
micelle. The grease and oil are
binds soil to fabrics (or skin)
removed when the whole micelle
All detergents include a long, nonpolar,
dissolves in water and is removed
from the fabric or skin.
hydrocarbon “tail” holding a very polar or ionic
“head”.
136
137
(a) A representation of a micelle. The nonpolar tails “dissolve” in one
another in the center of the cluster and the polar heads on the outside
interact favorably with the polar water molecules. (b) Attachment of
soap or detergent molecules to a droplet of oily dirt to suspend it in
138
water.
28