Separation of mixture

• When the components of a mixture are to be separated from each other, it is very important to look at the characteristic properties of each substance in order to decide how to separate them

Properties to consider:

Property Separation method

Size of particles • Sedimentation

• filtrationDensity of a substance

• Sedimentation

• decantationBoiling point of a substance

• distillation

Sedimentation and decantation

(settling and pouring out)

• The size of the particles of a substance have to be large enough to settle to the bottom of the container (sedimentation=settling)

• The larger the size of the particles, the faster they settle to the bottom of the container

• The liquid above the the sediment particles should be quite clear and can be poured off easily (decantation=pouring off)

Limitations• If the size of the particles is too small,

it may take too long for them to settle to the bottom of the container and the particles may also be easily stirred up if we try to pour off the liquid above the particles

• This method does NOT work for solutions

Examples• Pulp sediments to the bottom of the

orange • Vinegar separate from oil in salad

dressing• In water treatment plants, debris

separates from water in a sedimentation basin

Filtration• The size of the particles of a

substance have to be too large to pass through the holes of a filter

• Residue: is what is left on the filter• Filtrate: the liquid that passes

through the filter

Limitations• Filtration takes time and may take

longer as the residue accumulates on the filter

• This method does NOT work for solutions

Examples• Making filtered coffee• A vacuum cleaner traps dust in its filter• A colander holds food and allows water

to pass through

Distillation (boiling)

• The substance in the mixture with the lowest boiling point will evaporate first and then condense in a cooled container

• Distillate: the liquid that evaporates• Residue: The substance left behind in

the original container

Limitations • This method CANNOT be used if 2

substances have the same boiling point

examples• Making distilled water in the water• Producing gasoline from potroleum