Separation of Mixtures
Mixtures may be separated by many
different techniques based on differing
physical and/or chemical properties
What’s a mixture?
• A mixture consists of two or more pure
substances combined physically
• A mixture has variable composition
– As opposed to pure substances, which always
have the same composition (elements or
compounds)
Sorting
Simply picking apart
the different
components
This can be easy and
obvious…
Sort the laundry into
colored and whites!
Or it can be
challenging…
An organic chemist
who used a
microscope to sort out
mirror image crystals
of a compound
Sieving
Using screens to
sort by size
Sifting flour or
sugar…
or gold nuggets
or soil
Filtration
Particles
separated from
liquid or gas
Coffee,
Furnace,
Lab filter setup
with funnel
Decantation
Pouring liquid off
of settled mixture
Or remove a layer
of liquid
Wine from
sediment
Cleaner water in
water treatment
plant
Magnetism
Iron from
aluminum, plastic,
and paper
at recycling plant
Cow magnets!
Density
Different types of
plastic at recycling
plant
Oil on water
Dissolving
If one substance
dissolves and another
doesn’t
Salt and sand…salt
dissolves in
water…sand
doesn’t…sand settles
Tea flavor from tea
leaves…flavor and
color dissolves…tea
leaves don’t…the bag
acts as a filter
Centrifugation
Spinning to pull
heavier part of
mixture to bottom
Blood cells are
separated
from serum
The spin cycle in
the washer
removes water
from clothes
Maybe even DIRT
from clothes 
Distillation
Differences in
boiling points can
be used to
separate liquids
(differences in
freezing and
sublimation points
may also be used )
Alcohol in stills
Oil refineries
Purifying gases
Chromatography
From “chroma” meaning color
because this technique was
first used for dyes
A mobile phase carries
sample along over or
through a stationary
phase.
Components are
separated because
they have different
attractions for the
phases.
Paper chromatography to
separate pigments in ink is
one example
There are many variations for
many different mixtures
Evaporation
Remove a liquid
from a solid
Sea salt isolated by
evaporating sea
water in shallow
ponds
Solids may also be
purified by recrystallization
Shaking
Motion… a dog
shaking to remove
water 
Gravity/density…
gentle shaking causes
dense items to sink
and less dense to rise
Almost any difference in physical
properties can be used to separate
mixtures physically
Differences in chemical properties can
also be used to separate mixtures
chemically.
Identify the physical property and the
chemical property that are being used
to clean up this oil spill
Single stream recycling:
How do they sort this mess out?
Lots of
ingenuity…and
knowledge of
physical and
chemical
properties!
Separation challenges
Articles from 2013 and
2014 about cleaning up
water used for hydraulic
fracturing to get natural
gas…fracking
• Frack water cleanup
• Fracking Water
Recycling
SEPARATION TECHNIQUES
are limited only by people’s
ingenuity and imagination!