Methods of Separating Mixtures
•
•
•
•
•
•
•
Magnet
Filter
Decant
Evaporation
Centrifuge
Chromatography
Distillation
Mixture of
solid and
liquid
Filtration
separates
a liquid
from a
solid
Stirring
rod
Funnel
Filter paper
traps solid
Filtrate (liquid
component
of the mixture)
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 40
Chromatography
• Tie-dye t-shirt
• Black pen ink
• DNA testing
– Tomb of Unknown Soldiers
– Crime scene
– Paternity testing
Paper Chromatography
Separation by Chromatography
sample
mixture
a chromatographic column
stationary phase
mobile phase
selectively absorbs sweeps sample
components
down column
http://antoine.frostburg.edu/chem/senese/101/matter/slides/sld006.htm
detector
Separation by Chromatography
sample
mixture
a chromatographic column
stationary phase
mobile phase
selectively absorbs sweeps sample
components
down column
http://antoine.frostburg.edu/chem/senese/101/matter/slides/sld006.htm
detector
Ion chromatogram of orange juice
detector
response
K+
Na+
0
5
Mg2+ Fe3+
10
15
time (minutes)
20
Ca2+
25
Setup to heat a solution
Ring stand
Beaker
Wire gauze
Ring
Bunsen burner
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 42
A Hero’s Fountain
Glass retort
mixture for distillation
placed in here
long spout helps
vapors to condense
Eyewitness Science “Chemistry” , Dr. Ann Newmark, DK Publishing, Inc., 1993, pg 13
Furnace
A Distillation Apparatus
thermometer
liquid with a solid
dissolved in it
condenser
tube
distilling
flask
Dorin, Demmin, Gabel, Chemistry The Study of Matter , 3rd Edition, 1990, page 282
hose connected to
cold water faucet
receiving
flask
pure
liquid
The solution is boiled and steam
is driven off.
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 39
Salt remains after all water is
boiled off.
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 39
No chemical change occurs
when salt water is distilled.
Distillation
(physical method)
Salt
Saltwater solution
(homogeneous mixture)
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 40
Pure water
Separation of a sand-saltwater
mixture.
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 40
Separation of Sand from Salt
1.
Gently break up your salt-crusted sand with a plastic spoon.
Follow this flowchart to make a complete separation.
Saltcrusted
sand.
Calculate
weight of
salt.
Weigh the
mixture.
Weigh
sand.
Pour into
heat-resistant
container.
Fill with
water.
Stir and let
settle 1
minute.
Decant
clear
liquid.
Dry
sand.
No
2. How does this flow
chart insure a complete
separation?
Evaporate
to
dryness.
Yes
Repeat
3 times?
Wet
sand.
Four-stroke Internal
Combustion Engine
Different Types of Fuel Combustion
Gasoline (octane)
2 C8H18 + 25 O2  16 CO2 + 18 H2O
Methanol (in racing fuel)
__CH3OH +__O2 __CO2 +__H2O
Combustion Chamber
-The combustion chamber is the area where compression and
combustion take place.
-Gasoline and air must be mixed in the correct ratio.
The Advantages of Methanol Burning Engines
•Methanol can run at much higher compression ratios,
meaning that you can get more power from the engine on
each piston stroke.
•Methanol provides significant cooling when it evaporates in
the cylinder, helping to keep the high-revving, highcompression engine from overheating.
•Methanol, unlike gasoline, can be extinguished with water if
there is a fire. This is an important safety feature.
•The ignition temperature for methanol (the temperature at
which it starts burning) is much higher than that for gasoline,
so the risk of an accidental fire is lower.
A Race Car - Basic Information
•At 900 hp, it has about two to three times the horsepower of a "highperformance" automotive engine. For example, Corvettes or Vipers
might have 350- to 400-horsepower engines.
•At 15,000 rpm, it runs at about twice the rpm of a normal automotive
engine. Compared to a normal engine, an methanol engine has larger
pistons and the pistons travel a shorter distance up and down on each
stroke.
•The motor is lighter. This lowers their inertia and is another factor in the
high rpm.
Centrifugation
• Spin sample very rapidly:
denser materials go to
bottom (outside)
• Separate blood into serum
and plasma
– Serum (clear)
– Plasma (contains red blood
cells ‘RBCs’)
AFTER
Before
Serum
Blood
RBC’s
• Check for anemia (lack of iron)
A
B
C
Water Molecules
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 8
The decomposition of two water
molecules.
Water
molecules
Diatomic
oxygen molecule
+
Diatomic
hydrogen molecules
Electric
current
2 H2O

O2
+
2 H2
Electrolysis
“electro” = electricity
“lysis” = to split
H2O(l)
water
*H1+
Water
Oxygen
gas forms
Hydrogen
gas forms
O2 (g) + 2 H2 (g)
oxygen
hydrogen
*Must add acid catalyst
to conduct electricity
Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 32
Source of
direct current
Electrode
Electrolysis of Water
D.C. power
source
oxygen
gas
hydrogen
gas
anode
cathode
Half reaction at the cathode (reduction):
4 H2O + 4 e -  2 H2 + 4 OH 1Half reaction at the anode (oxidation):
2 H2O  O2 + 4 H 1+ + 4 e -
water
Reviewing Concepts
Physical Properties
• List seven examples of physical
properties.
• Describe three uses of physical properties.
• Name two processes that are used to
separate mixtures.
• When you describe a liquid as thick, are
you saying that it has a high or low
viscosity?
Reviewing Concepts
Physical Properties
• Explain why sharpening a pencil is an
example of a physical change.
• What allows a mixture to be separated by
distillation?
Reviewing Concepts
Chemical Properties
• Under what conditions can chemical
properties be observed?
• List three common types of evidence for a
chemical change.
• How do chemical changes differ from
physical changes?
Reviewing Concepts
Chemical Properties
• Explain why the rusting of an iron bar
decreases the strength of the bar.
• A pat of butter melts and then burns in a
hot frying pan. Which of these changes is
physical and which is chemical?