methods of separating mixtures

Methods of Separating Mixtures

• Magnet• Filter• Decant• Evaporation• Centrifuge• Chromatography• Distillation

Filtration separates

a liquid from a solid

Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 40

Mixture ofsolid andliquid Stirring

rod

Filtrate (liquidcomponentof the mixture)

Filter papertraps solid

Funnel

Chromatography• Tie-dye t-shirt

• Black pen ink

• DNA testing– Tomb of Unknown Soldiers– Crime scene – Paternity testing

Paper Chromatography

Separation by Chromatography

samplemixture

a chromatographic column

stationary phaseselectively absorbs

components

mobile phasesweeps sampledown column

detector

http://antoine.frostburg.edu/chem/senese/101/matter/slides/sld006.htm

Ion chromatogram of orange juice

time (minutes)

dete

ctor

re

spon

se

0 5 10 15 20 25

Na+

K+

Mg2+ Fe3+

Ca2+

Setup to heat a solution


Ring stand

Beaker

Wire gauze

Ring

Bunsen burner

long spout helpsvapors to condense

mixture for distillation placed in here

Furnace

Glass retortA Hero’s Fountain

Eyewitness Science “Chemistry” , Dr. Ann Newmark, DK Publishing, Inc., 1993, pg 13

A Distillation Apparatus

liquid with a soliddissolved in it

thermometer

condenser

tubedistillingflask

pure liquid

receiving flaskhose connected to

cold water faucetDorin, Demmin, Gabel, Chemistry The Study of Matter , 3rd Edition, 1990, page 282

The solution is boiled and steam is driven off.


Salt remains after all water is boiled off.


No chemical change occurs when salt water is distilled.


Saltwater solution(homogeneous mixture)

Distillation(physical method)

Salt

Pure water

Separation of a sand-saltwater mixture.


Separation of Sand from Salt1. Gently break up your salt-crusted sand with a plastic spoon.

Follow this flowchart to make a complete separation.

Salt-crusted

sand.

Drysand.

Wetsand.

Weigh themixture.

Decant clearliquid.

Evaporateto

dryness.

Pour intoheat-resistant

container.

Fill with water.

Stir and letsettle 1 minute.

Weighsand.

Calculateweight of

salt.

Repeat3 times?Yes

No

2. How does this flowchart insure a completeseparation?

Four-stroke Internal Combustion Engine

http://en.wikipedia.org/wiki/Internal_combustion_engine

Different Types of Fuel Combustion

2 C8H18 + 25 O2 16 CO2 + 18 H2O

__CH3OH +__O2 __CO2 +__H2O

Methanol (in racing fuel)

Gasoline (octane)

Combustion Chamber-The combustion chamber is the area where compression and combustion take place.

-Gasoline and air must be mixed in the correct ratio.

•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, high-compression 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.

The Advantages of Methanol - Burning

Engines

•At 900 hp, it has about two to three times the horsepower of a "high-performance" 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.

A Race Car - Basic Information

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’)• Check for anemia (lack of iron)

Blood

RBC’s

Serum

A B C

AFTERBefore

Water Molecules


The decomposition of two water molecules.

2 H2O O2 + 2 H2

Electriccurrent

Watermolecules

Diatomic Diatomicoxygen molecule hydrogen molecules+

Electrolysis

*Must add acid catalyst to conduct electricity

*H1+

water oxygen hydrogen

“electro” = electricity “lysis” = to split


Water

Hydrogengas forms

Oxygengas forms

ElectrodeSource ofdirect current

H2O(l) O2 (g) + 2 H2 (g)

Electrolysis of Water

Half reaction at the cathode (reduction): 4 H2O + 4 e - 2 H2 + 4 OH 1-

Half reaction at the anode (oxidation): 2 H2O O2 + 4 H 1+ + 4 e -

hydrogengas

cathode

oxygengas

anode

D.C. powersource

water

Reviewing ConceptsReviewing ConceptsPhysical 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 ConceptsReviewing ConceptsPhysical Properties

• Explain why sharpening a pencil is an example of a physical change.

• What allows a mixture to be separated by distillation?

Reviewing ConceptsReviewing ConceptsChemical 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 ConceptsReviewing ConceptsChemical 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?

methods of separating mixtures

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