Separating Techniques

Question 1

What is a mixture

Answer 1

2 or more elements or compounds not chemically bonded

Question 2

Simple distillation use

Answer 2

To separate a solvent from a solution
used for producing water from a salt solution

Question 3

Processes of simple distillation

Answer 3

Works a the dissolved solute has a much higher boiling point than the solvent

Heat the solution then the vapour will evaporate and the gas is moved away cooled and condensed

Leaving a pure liquid

Question 4

Fractional distillation

Answer 4

Separate all pure liquid from a mixture of liquids

Must have different boiling points

Question 5

Fractional vs simple distillation

Answer 5

Simple - used to separate a solvent from a solution

Fractional is use to separate different liquids from a mixture of liquids using boiling points

Question 6

Fractional distillation work with oil

Answer 6

Oil is heated up until it evaporates

Vapours rise up the column and condese at different fractions

Question 7

Filtration

Answer 7

Used to separate an insoluble solid from a liquid

Question 8

How to separate an insoluble substance from a solution

Answer 8

Place filter paper in a funnel

Pour the solution through a funnel

The insoluble substance will collect on the filter paper and the solution will collect in conical flask

Question 9

When is crystallisation used

Answer 9

To separate a soluble solid from a solution

if the solid breaks down due to heat

Question 10

How could u separate a soluble solid from a solution if it breaks down due to heat

Answer 10

Crystallisation

Pour a solution into an evaporating dish

Heat gently

When crystals form remove the dish from the heat and leave to cool

Once cold filter the crystals out the solution g and leave in a warm place to dry

Question 11

Process used to identify soluble substances

Answer 11

Chromatography

Question 12

How does paper chromatography work

Answer 12

The mobile phase - solvent - moves through the stationary phase - paper

Mobile phase ( solvent ) moves up the paper

Compounds react differently with each phase so will move different distances throughout the stationary phase

Question 13

How can chromatography show the compositions of a mixture

Answer 13

Different coloured substances in the mixture separate as they have different solubilities in the solvent and travel different rates

Question 14

Why is pencil used to draw a line

Answer 14

It won’t effect the experiment as pencil is insoluble in the solvent

Question 15

Why should the solvent be no deeper than 1 cm in chromatography

Answer 15

If it is deeper it will wash away the substances placed on the line of the paper

Question 16

Why should you use a lid when doing paper chromatography

Answer 16

To prevent solvent evaporation

Question 17

How many sports does a pure vs impure substance produce in chromatography

Answer 17

Pure substance one spot

Impure substance - contains more than one compound so will produce more spots

Question 18

What is rf value

Answer 18

The rf value is the ratio between distance travelled by the dissolved substance be the distant travelled by the solvent

Question 19

How do you calculate Rf

Answer 19

Distance travelled by substance /distance travelled by solvent.

Question 20

Where do you measure the distance travelled by the substance

Answer 20

From the pencil base line to the middle spot of the substance

Question 22

How can you use chromatography to see if a certain substance is present in a mixture

Answer 22

Runs pure sample of this substance alongside the unknown mixture

If the pure substances matches the value of one of the spots from the mixture then it is likely present

Question 23

Which substances travel further in chromatography

Answer 23

Higher solubility as they stay dissolved in the solvent for longer

Question 24

How could u separate salt from a mixture of salt and sand

Answer 24

Salt is soluble in water sand isn’t

Add water to a mixture

Filter the diluting to remove the insoluble sand evaporate the water to collect salt crystals

Question 25

How can liquids with 2 different densities be separated

Answer 25

Naturally separate into 2 layers Use a flask with a two on the bottom Open the tap to collect the bottom liquid - higher density

Question 26

What is potable

Answer 26

Safe to drink

Question 27

How can east and gounf water be made potable

Answer 27

Sedimentation- large insoluble particles sink to the bottom after the water is left still for a while Filtration- removes small insoluble particles by passing water through layers of sand and filters Chlorination - kills bacteria and micro organisms which are too small to be removed by filtration

Question 28

How can sea water be made potable

Answer 28

Distillation Filter to remove insoluble particles Boil Cool and condense the water vapour

Question 29

Issues around making seawater potable

Answer 29

Extremely expensive as it cost a lot of energy to boil large volume of water In we’re what wter is toxic due to high concentration of salt so must be disposed carefully

Question 30

What is deionised water

Answer 30

Water that has had metallic ions removed such as copper

Question 31

Why is deionised water used in experimental analysis

Answer 31

Used to event ions in the water interacting with the substance under analysis If not deionised false positives may be produced