Chapter 4 S1 Science Separation Techniques

Question 1

What is sublimation used for?

Answer 1

To separate substances that sublime

Question 2

What is the definition of sublimation?

Answer 2

A change in physical state from solid directly to gas, without going through the liquid state

Question 2

What is the 1st step of sublimation?

Answer 2

1. set up the apparatus (refer to notes :3)

Question 3

What is the 2nd step of sublimation?

Answer 3

2. Use a filter funnel to cover the evaporating dish

Question 4

What is another use of sublimation?

Answer 4

To purify compounds

Question 4

What is the 3rd step of sublimation?

Answer 4

3. Heat the mixture in an evaporating dish

Question 4

What is the 4th step for sublimation? (+ explanation)

Answer 4

4. The subsyance in the evaporating dish sublimes and turns into vapour.
   The vapour will then be converted back to form a solid on the insides of the funnel; the substance is called the sublimate.

Question 5

What are some examples of substances that sublime?

Answer 5

Ammonium chloride, dry ice (solid carbon dioxide). solid iodine crystals and naphthalene

Question 5

What is the 1st principle of filtration?

Answer 5

1. Filter paper functions as the filter. The filter should have small pores that allow particles smaller than the pores to pass through and not particles bigger than the pores

Question 5

What can sublimation do?

Answer 5

Sublimation can separate 2 solid substances when one is able to sublime upon heating while the other cannot.

Question 5

What is filtration used for?

Answer 5

To separate an insoluble solid from a liquid

Question 6

What is the 2nd principle of filtration?

Answer 6

2. When the mixture is poured over the filter, liquid (particles are smaller than pore size) passes through the pores and form the filtrate. Solids (particles are larger than the pore size) are unable to pass through the pores and remain behind to form the residue.

Question 7

What is simple distillation used for?

Answer 7

To separate a pure liquid from a solution

Question 8

What is an important property of the constituents for distillation?

Answer 8

boiling point

Question 9

what is the 1st precaution of simple distillation including purpose?

Answer 9

1. addition of boiling chips to the mixture
   -to ensure smooth boiling by reducing the bumping of the liquid

Question 10

what is the 2nd precaution of simple distillation including purpose?

Answer 10

2. position of the thermometer bulb
   -it is placed near the opening of the condenser to measure the temperature of the vapour accurately. This also helps to determine the identity and purity of the distillate

Question 11

what is the 4th precaution of simple distillation including purpose?

Answer 11

4. receiving flask
   -a conical flask must be used because the narrow neck can reduce loss of the distillate through splashing

Question 11

what is the 3rd precaution of simple distillation?

Answer 11

3. direction of water flow in condenser

Question 12

what is an important property of constituents in paper chromatography?

Answer 12

the different substances have different solubility in a solvent

Question 12

what is the purpose of the 3rd precaution of simple distillation?

Answer 12

-cooling water should enter the condenser jacket through the lower tube and leave by the upper tube
-direction of water flow is opposite to the direction that vapour moves in the condenser to ensure efficient cooing & complete condensation of the vapour

Question 13

what is paper chromatography used for?

Answer 13

To separate & identify solutes in a mixture by dissolving it in a solvent & allowing them to move along the chromatography paper at different speeds

Question 13

what is evaporation used for?

Answer 13

to separate a dissolved solid from a solution by evaporating the solvent (with or without heating)

Question 13

what is the 1st precaution of paper chromatography including explanation?

Answer 13

1. starting line has to be drawn in pencil; not ink
   -ink consists of a mixture of colours which may dissolve in the solvent and interfere with the results

Question 13

what is magnetic attraction used for?

Answer 13

to separate magnetic materials from non-magnetic materials

Question 13

what is the 2nd precaution of paper chromatography including explanation?

Answer 13

2. start line must be above the solvent level at the start of the experiment
   -to prevent spots from dissolving in the solvent

Question 14

what is the 3rd precaution of paper chromatography including explanation?

Answer 14

3. only a small spot of sample must be placed at the start line
   -to prevent overlapping and smudging of components

Question 15

what is the 4th precaution of paper chromatography including explanation?

Answer 15

4. the solvent front must be allowed to reach near the top of the chromatography paper
   -to ensure complete separation of the mixture

Question 15

how do we locate and identify colourless spots of a sample?

Answer 15

the chromatogram is sprayed with a locating agent that can react with the substances on the chromatogram to produce a coloured product

Question 15

what is the equation of Rf value?

Answer 15

distance from start line to spot over distance from start line to solvent front

Question 16

what is the principle of separation of magnetic attraction?

Answer 16

magnetism