Separation Techniques (1)

Question 1

Mixture

Answer 1

• A mixture is made up of components not chemically combined together, e.g. ink, fizzy drinks, mineral water, crude oil, air.

Question 2

Mixtures continued…

Answer 2

• The components of a mixture can be separated by several methods or techniques.
• Each separation technique makes use of differences in the physical properties of the components.

Question 3

Methods of Separating Mixtures

Answer 3

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

Question 4

Magnetic Attraction

Answer 4

• Used to separate magnetic materials, e.g. iron, steel, nickel, cobalt from non-magnetic ones in a mixture.
  e. g. separating iron filings from sulphur powder

Question 5

Applications of Magnetic Attraction

Answer 5

1. Electromagnets are used to remove steel and iron scrap at the junk-yard.
2. In hospitals, magnets are often used to remove iron splinters from a patient’s eyes.

Question 6

Evaporation to Dryness

Answer 6

• Used to separate a dissolved solid (solute) that does not decompose on heating from a solution.
  e. g. common salt from a salt solution

Question 7

Procedure of Evaporating a Solution

Answer 7

1. Pour the solution into an evaporating dish.
2. Heat the solution to dryness to evaporate away the solvent, leaving behind the solute.
3. Make the Bunsen flame smaller when almost all the solvent has been evaporated away to reduce spitting.

Question 8

Applications of Evaporation

Answer 8

• drying wet clothes
• drying hair with a hair dryer
• obtaining common salt from the sea

Question 9

Crystallization

Answer 9

• Process to obtain a solid that decomposes on heating from its solution.
  e. g. sugar crystals from sugar solution and copper(II) sulfate crystals from copper(II) sulfate solution

Question 10

Filtration

Answer 10

• Separates a liquid from a solid.

Question 11

residue

Answer 11

• insoluble solid that remains on the filter paper

Question 12

filtrate

Answer 12

• liquid that passes through

filtrate can be water, any other solvent, or a solution

Question 13

Applications of Filtration

Answer 13

• hair in our nostrils
• trap the dust particles that we breathe and allow only clean air to pass through
• air filters in air conditioners
• remove solid impurities from air
• oil and air filters in cars
• remove solid impurities found in engine oil and air

Question 14

Simple Distillation

Answer 14

• Process used to separate a pure liquid (solvent) from a solid-liquid solution.
  e. g. pure water can be distilled from soft drinks, sea water, etc.

Question 15

Distillation Apparatus

Answer 15

• 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.

Question 16

Fractional Distillation

Answer 16

• Process can be used to separate miscible liquids with different boiling points.
• Liquid with lower boiling point will vaporize first.
  e. g. to separate alcohol and water

Question 17

Industrial Applications of Fractional Distillation

Answer 17

• oil refineries
• separating the various components of crude oil or petroleum
• industrial supplying oxygen to hospitals, shipyards, etc.
• separating the components of air

Question 18

Paper Chromatography

Answer 18

• Process used to separate the different components in a liquid mixture.
  For example it can be used
  1. to separate the different colored components that make up black ink
  2. to detect tiny amounts of drugs or certain other chemicals in urine samples

Question 19

Applications of Paper Chromatography

Answer 19

• analyzing ink dyes for forgery cases
• analyzing food dyes to ensure that only permitted colorings are used in foodstuffs
• checking whether pesticides on vegetables exceed safe levels
• detecting trace levels of drugs in urine samples

Question 20

Centrifugation

Answer 20

• Spin sample very rapidly: denser materials go to the bottom (outside)
• Separate blood into serum and plasma
• Plasma = less dense
• Erythrocytes = red blood cells
  
  • Check for anemia (lack of iron)

Question 21

Applications of Centrifugation

Answer 21

• It is used for:
• Separating cream from milk and butter from curd in dairies or at home.
• In washing machines to squeezing out water from wet clothes.
• In diagnostic laboratories for testing blood/urine.

Question 22

Separating Funnel

Answer 22

• When two immiscible liquids are mixed together they eventually form layers, if left to stand. The less dense liquid forms a layer above the more dense liquid.

Question 23

Decantation

Answer 23

• Beaker x2
• Sand
• Water
• Glass rod

Question 24

What is Sieving?

Answer 24

• Is used for separating coarse from fine parts of loose matter.

Question 25

What is Straining?

Answer 25

• It is to pour a mainly liquid substance through a porous device or material in order to separate out any solid matter.

Question 26

What is Winnowing?

Answer 26

• Is separating the chaff from the grains by wind.

Question 27

Why do we put filters in our faucets?
A. To separate the impurities from water
B. To purify the water
C. To kill the germs in the water

Answer 27

A. To separate the impurities from water

Question 28

If you were given a mixture of sulphur and iron filings, how will you separate the two kinds of components?
A. Use a mirror
B. Use a magnet
C. Use a Bunsen burner
D. Either a or b

Answer 28

B. Use a magnet

Question 29

You accidentally drop a box of pins on sandy ground. What is the fastest way of recovering the pins from the ground?
A. Use a water heater
B. Use magnet
C. Throw water on the ground
D. Use a filter paper

Answer 29

B. Use magnet