seperating techniques

Question 1

what’s a mixture?

Answer 1

the mixture of different substances where no chemical reaction has occurred

Question 2

what’s the mixture of iron and sulphur?

Answer 2

the iron is grey, sulphur is yellow
the iron reacts with dilute hydrochloric acid producing hydrogen
sulphur doesn’t react with acid
the compound of iron sulfide reacts with acids to produce poisonous hydrogen sulfide gas, which smells of eggs

Question 3

what’s the mixture of hydrogen and oxygen?

Answer 3

colourless gas that explodes when you put a flame to it

Question 4

how can mixtures be separated?

Answer 4

by physical means, like change in temperature or dissolving part of mixture
ways that don’t involve any chemical reactions

Question 5

how do you separate the mixture of sulphur and iron?

Answer 5

use a magnet

Question 6

how do you separate hydrogen gas and oxygen?

Answer 6

physical process
oxygen condenses into liquid at a higher temperature than hydrogen
liquid oxygen and hydrogen gas

Question 7

what’s different about the boiling point of pure substances and mixtures?

Answer 7

pure substances - melt and boil at fixed temperatures
mixtures - melt and boil over a range of temperatures

presence of impurities lowers the melting point and raises the boiling point

Question 8

what’s filtration?

Answer 8

can be used to separate a solid from a liquid
substance that is left in filter paper is called residue
the liquid that comes through is called filtrate

Question 9

what equipment is needed for filtration?

Answer 9

filter paper
funnel
beaker

Question 10

what’s crystallisation?
example

Answer 10

used to separate a solute from a solution

seperate sodium chloride from sodium chloride solution
solution heated in an evaporation basin to boil off the water until a saturated solution is formed
can be tested by dipping a glass rod into the solution and seeing if crystals quickly form on it’s surface
bunsen burner is then turned off and the crystals form as the water continues to evaporate and solution cools
crystals can nor be removed from mixture using filtration

Question 11

what equipment is needed for crystallisation?

Answer 11

bunsen burner
tripod
gauze
evaporation basin
glass rod

Question 12

what’s simple distillation?

Answer 12

used to separate the components of a solution

water boils and condenses back to a liquid by the condenser to a beaker
salt remains in flask

Question 13

what’s the equipment needed for simple distillation?

Answer 13

conical flask
bung
gauze
bunsen burner
condenser
beaker

Question 14

what’s fractional distillation?

Answer 14

used to separate a mixture of liquids
separated by taking advantage of their boiling points
both liquids boil but control temperature carefully using thermometer

Question 15

what equipment is needed for fractional distillation?

Answer 15

thermometer
fractional column
flask
gauze
bunsen burner
condenser
beaker

Question 16

what’s paper chromatography?

Answer 16

used to separate a variety of mixtures of coloured inks or food colouring
used to separate colourless substances like sugars too

Question 17

what’s the method for paper chromatography?

Answer 17

1. draw a line in pencil across a piece of chromatography paper - do not use pen as its inks will move up the paper with the solvent
2. place the dye dots on the pencil line and let dry
3. suspend chromatography paper into beaker that contains solvent that only the bottom bit of paper goes into - important that solvent is below pencil line so inks don’t just dissolve into solvent
4. put a lid on the breaker so that atmosphere becomes saturated with solvent , and stopping evaporation of the solvent from the paper
5. when solvent has moved up paper and reached 1cm away from the top remove paper from beaker and draw a line using a pencil to show where solvent got to
6. leave paper to dry so solvent evaporates

Question 18

what’s the highest level of the solvent on the paper at any time called?

Answer 18

solvent front

Question 19

what’s the pattern you get from chromatography paper?

Answer 19

chromatogram