Seperation Techniques

Question 1

Describe à mixture

Answer 1

It’s when two or more elements/compounds are physically mixed

They are not chemically bonded

Thy can be separated using physical methods and (no chemicals required)

The properties of a mixture are just the properties of the separate elements or compounds

Question 2

How do you perform paper chromatography

Answer 2

Draw a line near the bottom of a sheet of filter paper in pencil

Add a spot of ink to the line of the pencil and then place sheet into a solvent like water

Ensure ink isn’t touching the solvent directly
Place a lid on the beaker to prevent the ink from evaporating,

If a ink is in soluble it will stay on the line, but if it is soluble the ink will seperate out at different rates and will form a spot in different places, 1 dot per dye in ink

When solvent nearly reaches the top of the paper leave it out to dry, and then you will have a chromatogram

Question 3

How would you seperate the dyes out in ink?

Answer 3

Chromatography

Question 4

When would you use filtration

Answer 4

When you are trying to seperate an insoluble solid from a liquid

Question 5

How does filtration work

Answer 5

You get a funnel, filter paper and a beaker

Fold filter paper into a cone shape then put in funnel

Then place funnel over beaker

And pour the solution into the funnel

Question 6

What two ways can be used to separate a soluble substance from a solution

Answer 6

Evaporation

Crystallisation

Question 7

How does evaporation work (describe it)?

Answer 7

You pour the solution into an evaporation dish

Slowly heat the solution, solvent will evaporate leaving a more concentrated solution eventually crystals will bring to form

Keep heating until you get dry crystals in the evaporation dish

Question 8

How does crystallisation work?

Answer 8

Pour solution into evaporation dish

Gently heat, so solvent evaporated and solution gets more concentrated

When that happens or you see crystals begin to form stop heating and leave the dish out to cool

Crystals should form as it becomes insoluble in the cold highly concentrated solution

Filter the crystals out of the solution and l ave them in a warm place to dry

Question 9

When can’t evaporation be used?

Answer 9

If the salt begins to decompose when it’s heated

Question 10

Describe the process of separate rock salt

Answer 10

Grind the mixture down so the small salt cyrstals will dissolve quickly

Then put the mixture into water and let it dissolve

Then filter the mixture, the dissolved salt in the water will go through the filter paper, while the left over sand molecules will be left in the filter paper

Then use evaporation to create dry crystals

Question 11

What is simple distillation?

Answer 11

It is used for separating a liquid out of a solution

Question 12

Describe how to perform simple distillation

Answer 12

Heat the solution

the vapour is then cooled, condenses and is collected in a separate beaker

Question 13

What is the problem with simple distillation

Answer 13

The boiling temperature of the solution and the liquid you want to separate have to be very different, otherwise they will both evaporate too close to each other and they will then both condense and mix together

Question 14

Can simple distillation be used to separate a solid and a liquid such as seawater?

Answer 14

YES

Question 15

What is fractional distillation? When would you use it?

Answer 15

It is used to separate liquids out of solutions, you would use it when two substances in the solution have very similar boiling points

Question 16

How does fractional distillation work? Describe

Answer 16

Put mixture in a flask and then stick a fractional column on top

The liquids evaporate at different temperatures

The lowest boiling point will go to the top of the coloumn then condense

Then the higher boiling point liquids will also evaporate but as the fractionating column is cooler nearer the top, the vapour will not go all the way to the top before condensing again

meaning you can collect several liquids in one column with very close boiling points

When the fist liquid is collected you can then raise the temperature until the next one reaches the top