C1.3/4- Separating Mixtures

Question 1

Mixture

Answer 1

• made up of 2/more substances that are not chemically combined
• chemical properties of each substance in the mixture remain unchanged

Question 2

Element

Answer 2

Made up of one type of atom only

Question 3

Atom

Answer 3

Smallest part of an element which can be recognised as that element

Question 4

Chemical compound characteristics

Answer 4

• has a fixed composition
• chemicals in a compound must be separated by a chemical reaction
• they have chemical bonds between the atoms of the different elements in a compound

Question 5

Fixed composition meaning

Answer 5

Ratio of elements present is always the same in any particular compound
I.e H20

Question 6

Mixture characteristics

Answer 6

• has no fixed composition
• different elements in a mixture can be separated more easily
• there are no chemical bonds between the atoms of different substances in the mixture

Question 7

Separating mixtures method

Answer 7

• by physical means
• using the differences in properties of each substances
• relying on properties like boiling points or magnetism

Question 8

Techniques to separate mixtures

Answer 8

• filtration
• crystallisation
• distillation
• chromatography

Question 9

Filtration

Answer 9

-separates substances that are insoluble in a particular solvent from solute

Question 10

Example of filtration method

Answer 10

1- fill up beaker with 50ml of water
2-pour 4-5 spatula scoops of rock salt and stir
3- outline a conical flask with filter paper and pour in solution
4-filtration will take place here, removing any insoluble matter on the paper and leaving the filtrate to pass through

Question 11

Filtration of rock salt: equipment

Answer 11

• beaker
• sodium chloride
• spatula
• conical flask
• filter paper
• rock salt

Question 12

Crystallisation

Answer 12

-usually used to separate salt and water solutions
-Done by:
Heating up the solution in an evaporating dish over a water bath
Then the heat should be removed allowing the remain water to evaporated at room temperature

Question 13

Distillation

Answer 13

• this process allow us to collect the solvent instead of letting it evaporate into the air
• allows us to purify water
• eg allows us to turn seawater into usable water

Question 14

Simple distillation

Answer 14

1- solution is heated to evaporate the solvent
2- vapour given off then enters the condenser so that it can be turned into a liquid
-it is the collected in a receiving vessel
-any remaining matter will be left in the heating flask

Question 15

Condenser

Answer 15

• outer glass tube

- has water flowing through it that acts as a ‘cooling jacket’ around the inner glass tube from the flask

Question 16

Solvent

Answer 16

The liquid in which the solute dissolved

-usually water

Question 17

Solute

Answer 17

The substance that dissolved into a liquid to form a solution

Question 18

Solutions

Answer 18

Mixture formed when a solute has dissolved in a solvent

Question 19

Soluble

Answer 19

Describes a substance that is able to dissolve

Question 20

Insoluble

Answer 20

Describes a substance that will not dissolve

Question 21

Fractional distillation

Answer 21

-separates mixtures of miscible liquids and liquids that have different boiling points

Question 22

Miscible

Answer 22

-Describes liquids that dissolve into each other or mix completely
-they will not form separate layers seen in immiscible mixtures
I.e oil+water

Question 23

Miscible liquid properties

Answer 23

-have different boiling points

Question 24

Fractional distillation method

Answer 24

• collect the liquid with the lowest boiling point first as it will evaporate first
• adding a fractionating column means that both vapours will pass through the beads
• but the substance with the higher boiling point will condense and fall back down
• while the liquid with the lower boiling point will pass through and enter the condenser

Question 25

Fractionating column

Answer 25

• a tall glass column filled with glass beads
• fitted right on top of the heating flask
• the higher up you go the lower the temperatures

Question 26

Fractional distillation use

Answer 26

• used to separate ethanol from fermented mixture in the alholic spirits industry
• then the ethanol is used as biofuel

Question 27

Paper chromatography

Answer 27

• used to separate substances from mixtures in a solution
• analyses colours in a solution (ink)
• works as some compounds in a mixture will dissolve better than others in the solvent selected

Question 28

Equipment for paper chromatography

Answer 28

• 1 pen
• 1 food colouring
• solution
• pencil
• chromatography paper
• capillary tube
• solvent

Question 29

Method for paper chromatography

Answer 29

1-draw a pencil line near the bottom of the sheet of paper
2-use a capillary tube to dab a spot of ink
3-place the paper standing upright in the beaker filled with the solvent
4-the paper will soak up the solvent and run through the spot of ink

Question 30

Why does paper chromatography work

Answer 30

• the higher up the substance is on the paper, the more soluble it is
• it separates the mixture to be identified