1 Separating Mixtures

Question 1

What is simple distillation?

Answer 1

Used for separating out a liquid from a solution

Question 2

Method: Simple Distillation

Answer 2

1. Solution is heated -> part of solution with lowest boiling point evaporates
2. Vapour is then cooled, condenses (turns back into a liquid) & is collected
3. Rest of solution is left behind in the flask

Question 3

What can you use simple distillation for?

Answer 3

to get pure water from sea water
-> water evaporates & is condensed & collected
-> eventually end up with just salt left in the flask

Question 4

What is a problem with simple distillation?

Answer 4

you can only use it to separate things with very different boiling points

Question 5

What is fractional distillation?

Answer 5

Used to separate a mixture of liquids

Question 6

What can you use fractional distillation for?

Answer 6

Fractional distillation of rude oil at a refinery

Question 7

Method: Fractional Distillation

Answer 7

1. Put mixture in a flask & stick a fractionating column on top -> then heat it
2. The different liquids will all have different BPs -> so they will evaporate at different temperatures
3. The liquid with the lowest BP evaporates first. When the thermometer temp matches the BP of this liquid -> it will reach the top of the column
4. Liquids with high BPS might also start to evaporate. But the column is cooler towards the top -> So they will only get part of the way up before condensing & running back down towards the flask

Question 8

What do you do when the first liquid has been collected?

Answer 8

You raise the temperature until the next one reaches the top

Question 9

What is filtration?

Answer 9

Used to separate an insoluble solid from a liquid

Question 10

What can you use filtration in?

Answer 10

In purification as well e.g. solid impurities can be separated out from a reaction mixture using filtration

Question 11

Method: Filtration

Answer 11

1. Put filter paper into a funnel
2. Pour mixture into it
3. The liquid part of the mixture runs through the paper, leaving behind a solid residue

Question 12

What is crystallisation?

Answer 12

Used to separate a soluble solid from a solution

Question 13

Method: Crystallisation

Answer 13

1. Pour solution into an evaporating dish + gently heat -> some of the water will evaporate + the solution will get more concentrated
2. Once some of the water has evaporated, or when you see crystals start to form (point of crystallisation), remove from heat
3. Leave solution to cool
   4.The salt should start to form crystals as it becomes insoluble in the cold, highly concentrated solution
4. Filter crystals out the solution + leave in a warm place to dry (or use a drying oven/desiccator)

Question 14

What is rock salt a mixture of?

Answer 14

A mixture of salt & sand (spread on roads in winter)