Mixtures and methods of separation
Mixtures vs. compounds
Mixture: made up of two or more substances that are NOT chemically
combined together
Compounds are made up of two or more elements which ARE chemically
combined together
How to separate mixtures
Filtration
- This is used to separate substances that are
insoluble (e.g. sand) in a particular solvent (water)
from that that are soluble (salt) in solvent
- You would put the solution through filter paper
which would leave sand on top but salt water
would be filtered out with the water into the
beaker
- The sand you collect (the filtrate) should be
washed with distilled water to remove any salt
solution left on it and the wet sand is then dried in
a warm oven to evaporate off any remaining water
in the sand to leave pure, dry sand
Crystallisation
- Separates a soluble solid from a solvent
- If you then wanted to obtain a pure sample of the
soluble solid (e.g. salt) from the solvent (e.g.
water) you would need to evaporate the water off
- The best way to do this is heating the solution in
an evaporating dish on a water bath
- Stop heating when the solution is at the point of
crystallisation which is when small crystals first
appear around the edge of the solution/when
crystals appear in a drop of solution extracted
from the evaporating dish
- The rest of the water is left to evaporate at room
temperature
Distillation
Mixtures vs. compounds
Mixture: made up of two or more substances that are NOT chemically
combined together
Compounds are made up of two or more elements which ARE chemically
combined together
How to separate mixtures
Filtration
- This is used to separate substances that are
insoluble (e.g. sand) in a particular solvent (water)
from that that are soluble (salt) in solvent
- You would put the solution through filter paper
which would leave sand on top but salt water
would be filtered out with the water into the
beaker
- The sand you collect (the filtrate) should be
washed with distilled water to remove any salt
solution left on it and the wet sand is then dried in
a warm oven to evaporate off any remaining water
in the sand to leave pure, dry sand
Crystallisation
- Separates a soluble solid from a solvent
- If you then wanted to obtain a pure sample of the
soluble solid (e.g. salt) from the solvent (e.g.
water) you would need to evaporate the water off
- The best way to do this is heating the solution in
an evaporating dish on a water bath
- Stop heating when the solution is at the point of
crystallisation which is when small crystals first
appear around the edge of the solution/when
crystals appear in a drop of solution extracted
from the evaporating dish
- The rest of the water is left to evaporate at room
temperature
Distillation
