Seperation Techniques

Question 1

Chromatography

Answer 1

Draw line at bottom of paper out of pencil as it is insoluble
Add a spot of ink on the line you want to separate
Place paper into a beaker of solvent
Place lid to stop evaporation
The solvent seeps up the paper carrying ink with it
Different dyes will move at different rates
Each dye will form a spot

Question 2

Filtration

Answer 2

Separates insoluble solids from liquids

Question 3

Two ways of separating soluble solids from a solution

Answer 3

Evaporating and crystallisation

Question 4

Evaporation

Answer 4

Pour solution in an evaporating dish
Slowly heat the solution until the solvent evaporated and the solution is concentrated
Keep hearing until all that is left is dry crystals

Question 5

What should you use evaporation

Answer 5

From separating soluble salts from a solution but can only be used if the salt doesn’t decompose when heated

Question 6

Crystallisation

Answer 6

Pour solution into an evaporating dish
Heat until some of solvent evaporated so it’s more concentrated
When crystals start to form remove from heat and cool
The salt forms crystals as it becomes insoluble in the cold highly concentrated solution
Filter crystals and leave in a warm place to dry.

Question 7

Separating rock salts through filtration and crystallisation

Answer 7

Grind mixture so dissolves easier
Dissolve into water and stir
Filter mixture so salt goes through with water and sand gets filtered out
Evaporate the water from the salt so it forms dry crystals

Question 8

Simple distillation

Answer 8

Used for separating liquids from a solution
Heat solution
Part of solution with lowest boiling point will evaporate first
The vapour cools and condensed and then is collected

This can only be used for liquids with very different boiling points

Question 9

Fractional distillation

Answer 9

Put mixture into a flask with fractioning column on top then heat it
They will evaporate at different boiling points

Liquid with lowest boiling point evaporate first
When thermometer in fractioning column is the same as the boiling point the liquid will travel to the top of the column
Other liquids might start to evaporate but will condense half way up the column as it is cooler
Once substance is collected heat up column

Question 10

How do you work out the rf value

Answer 10

Distance travelled by solution divided by distance travelled by solvent