Chemistry - Purification and Separation Methods


Separation techniques:

Separating a solid from a liquid: 

1. Decanting
- separating a dense, insoluble solid from a liquid (pour away)

2. Filtration
- separates insoluble solid + liquid   (eg. sand + water)
- residue and filtrate will be collected

3. Evaporation to dryness  (for substances which will not decompose upon heating) 
- dissolved solid from a solution 
- when we evaporate salt solution to dryness, we get the solid salt. 

4. Crystalization (substances that will decompose upon heating)"
- separates a solution (soluble solid + liquid) 
- water is removed by heating the solution
- heating is stopped at the stage when a hot saturated solution is formed.
- when cooled to room temp, the dissolved solid will be formed as pure crystals

Separating solids:

1. Filtration
- only if one of the solid is soluble and the other one is not.

2. Magnets

3. Sublimation:
- obtain the solid that sublimates

Separating a liquid from a solution:

1. Distillation
- getting pure water from seawater
- water in at the bottom,
- water out at the top
- this is to ensure cooling is efficient
- the thermometer should not be dipped into the solution,
this is to ensure that it measures the bp of the substance that is being distilled.  

2. Fractional distillation
- separates mixture of 2 miscible liquids(liquid with 2 diff. bp) (ethanol + water)
- obtain the liquid with the lower boiling point. 
- there's a fractionating column where the glass beads in it provide a large surface area for the vapour to condense on,
- and also allow vapours of liquid with higher bp to condense and re-enter the round bottomed flask. 

3. Separating funnel
- separates 2 immiscible liquid (oil + water)
- obtains oil and water separately  

volatile = liquid that evaporates easily, low boiling point

- separates mixtures of…


No comments have yet been made

Similar Chemistry resources:

See all Chemistry resources »See all Testing and analysing substances resources »