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SEPARATING MIXTURES(natalie) - Coggle Diagram
SEPARATING MIXTURES(natalie)
The need for Separating mixtures
Mixtures
2 substances
2+ substances
mixed
without chemical bonding
Purity of substances
is important
separated easily
into pure substances
by purification techniques
physical methods
Qn: Why are purification techniques classified as physical methods? :question:
Ans: A physical method only separates one substance from the other without any chemical changes.
No new products are formed in the process of separation. :check:
Sublimation
Solid-solid (without involving liquid)
Magnetic attraction
Filtration
Evaporation
Solid-liquid
Crystallisation
Chromatography
Simple distillation
Fractional distillation
Liquid-liquid
To obtain useful
substances
Air
useful substances
oxygen
have their respective applications
nitrogen
Seawater
table salt
preserving foods
cooking
Reservoirs
freshwater
drinking
Crude oil
useful fuels
petrol
kerosene
To study the
properties
Chemists
need pure substances
study their
chemical
properties
physical
To avoid unwanted
consequences
Impurities
drugs
can produce unwanted side effects
purity is VERY IMPORTANT
pharmaceutical
industry
food
The 4 National Taps
In SG
limited natural resource
WATER
protect our sovereignty
we need more reliable water resources
our PLAN
self-sufficient
in our water supply
The 4 National Taps
Water catchment areas
Desalinated water
Imported water from other countries
produce pure and safe drinking water
from
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NEWater
Separation of SOLID-SOLID mixtures
Sublimation
When a solid skips the liquid state and changes into a gas directly
during heating
one solid substance can sublime
E.g.
dry ice
iodine crystals
napthalene
mothballs
printing process
uses heat
transfers dye into paper/fabric
producing photographic prints
Magnetic attraction
Magnets
separate magnetic from non-magnetic
in a mixture
E.g.
iron fillings separated from sulfur powder in mixture
Magnetic materials
E.g.
iron
steel
nickel
cobalt
Scrap yards
strong electromagnet
salvage scrap iron & steel
from other junk materials
Mining
separate magnetic ores
from non-magnetic ores
Hospitals
remove iron splinters
from patients' eyes
Evaporation
Method
separate a dissolved solid
from a solution
by heating the solution
used if
the dissolved solid
heat-stable substance
strong heating.
no decomposition
Step 1
solution in evaporating dish
heated
solvent has dried up completely
Step 2
dried salt crystals
obtained the evaporating dish
Daily lives
common salt
obtained through evaporation
of seawater
evaporation
happens in living things
E.g.
evaporation of sweat
cools our body down
helps our bodies maintain a constant body temperature
on hot days
Filtration
separate an insoluble solid from a liquid
E.g.
o separate chalk powder from water
FEATURES
Residue
the insoluble solid
remains on the filter paper
Sand & Water
Residue
Sand
Filtrate
Water
Brewed coffee containing
ground coffee
Residue
Ground coffee
Filtrate
Brewed coffee
Insoluble silver chloride in
sodium nitrate solution
Residue
Silver chloride
Filtrate
Sodium nitrate solution
Filter funnel
Filter paper
pores
small liquid particles
pass through pores
large solid particles
trapped on filter paper
Qn: How can a filter paper separate an insoluble solid from a liquid?
Ans: Filter paper, very tiny pores.Particles that are smaller than the pores can pass through
the pores. The insoluble solids are larger than the pores, so they are trapped on the filter paper. :check:
filter an insoluble solid from a liquid
Filtrate
liquid that passes through the filter paper
Daily lives
Different types of fitration
separate different types of mixture
E.g.
Sink filter
removes large food particles
from entering the drainage system.
Tea bag
prevent tea grains
from spreading in water
Air-conditioner filter
removes dust particles
from incoming air
Sieve
filters
brewed coffee
from ground coffee
separates
Treatment of sewage
remove suspended solids and greases
from used water
before used water is discharged to seas & oceans
Treatment of rainwater
reservoir to drinking water
remove unwanted impurities
from rainwater
Filtration in the human BODY
mammalian kidneys
remove unwanted substances
from bloodstream
nostril hairs
removes dust and large suspended particles
from inhaled air
Reverse osmosis
The movement of water molecules from a high concentration to a low concentration across a membrane(filter)
used in SG
obtain desalinated water from seawater
a filtration method
involves a special type of membrane
removes unwanted large particles
E.g.
Salts from seawater
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Crystallisation
Method
separate a soluble solid
from its solution
which is not heat-stable
the soluble solid -> not heat-stable
decomposes on strong heating
obtain a soluble salt
from a solution
Step 1
salt solution is filtered
remove any solid impurities
Step 2
filtrate is heated
remove most of solvent
until solution becomes
saturated.
enables crystals to form easily.
Step 3
saturated solution is left to cool
allow the formation of large-size
crystals.
Step 4
crystals are filtered
crystals are washed
little cold distilled water
remove impurities
dried between filter paper
Solutes
hot water
higher solubility
cold water
lower solubility
E.g.
copper sulfate (the solute)
dissolved in 80*C water
is more than
copper sulfate
dissolved in 30*C water
of the same amount
hot saturated solution is cooled
cooled solution
holds less solute
compared to when solute was hot
excess solute
in a cooled solution
will be undissolved
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Daily lives
Crystallisation
important in food technology
E.g.
table sugar
sugar beet
CRYSTALLISATION
sugar cane
used in producing silicon
main component
most semiconductor devices
radio
computers
telephones
many other devices!
Separation of Liquid-liquid mixtures
Fractional distillation
process
separate two or more miscible liquids in a mixture
Miscible liquids
Miscible liquids are liquids which dissolve in each other to form a single layer.
E.g.
alcohol can be separated
from water in alcoholic drinks
Alcohol and water are miscible → they mix evenly.
Oil and water are not miscible (they’re immiscible) → they form layers.
fractional distillation works :check:
because
the 2 liquids have
different
boiling points
liquid with lower boiling point
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liquid with higher boiling point
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Daily lives
used in oil refineries
separate petroleum
useful products
petrol
kerosene
diesel oil
separate ethanol
produced in fermentation
use ethanol in alchaholic drinks
useful gases from air
oxygen
nitrogen
SEPARATED
air is liquefied
before fractional distillation is carried out
noble gases
THE PRINCIPLE OF DIFFERENT PURIFICATION
TECHNIQUES AT A GLANCE
Sublimation
Ability to sublime
Magnetic attraction
Ability to be attracted by magnets
Filtration
Size of particles
Evaporation
Soluble solid which is heat-stable
Crystallisation
Soluble solid which is not heat-stable
The principle to separate different substances in a mixture
Soluble
Salt is soluble in water → it dissolves.
Sugar is soluble in water.
Sand is not soluble in water → it doesn’t dissolve.
Simple distillation
Boiling point of a substance
Fractional distillation
Different boiling points of substances
Chromatography
separate and identify small amounts of substances
dissolved in a solvent
E.g.
dyes in coloured ink
separate different components in a mixture
different components
different solubility
different solubility in a solvent
move at different speeds
on the
chromatography paper
FEATURES
Lid
Starting line
Solvent
Solvent front
Components in the sample
Process
Step 1
small amount
concentrated sample
placed on starting line
of chromatographic paper
Step 2
the chromatographic paper
placed inside a beaker
that contains a solvent
solvent is below starting line
Step 3
solvent moves up the paper
SEPARATES
the sample
into its respective
components.
Step 4
chromatographic paper is removed
before
solvent reaches the edge
of the other end of the chromatographic paper
Precaution
1.
Draw starting line
pencil :check: pen :red_cross:
starting line
the location
where a sample is placed
Ink is made up of dyes which can dissolve in
the solvent and interfere the results.
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A pencil is an element, so it is not made of dyes and will not be separated by the solvent to interfere with the results.
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5.
The jar should be covered with a lid
when volatile solvent
E.g.
ALCOHOL
is used
It prevents the solvent from evaporating too
fast.
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It also ensures that the jar is saturated with
the solvent vapour.
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2.
Use fine capillary tubes
place a
small
sample
This prevents the overlapping of
components so that a clear and distinct lines
or spots can be obtained.
concentrated
3.
The solvent should be below
starting
line
This prevents the sample from dissolving into the solvent so that it can travel up the paper.
4.
The solvent front
as high as possible
the line
the solvent travels furthest
up the chromatographic paper
It ensures that the components in a sample
are fully separated.
How would it affect?
The result of the separated components
on the chromatography paper
Usefulness of chromatography
used to identify the contents of a mixture
used to test the purity of a substance.
Advantages of chromatography
Only a small amount of sample is required.
gives a fast and an accurate analysis of a sample.
able to separate complex mixtures such as food dyes
Daily lives
Food industries
used to analyse the safety levels of food sample
chromatography is used
E.g.
check the amount of pesticides on vegetables
ensure that they do not exceed the safety levels
check if the food sample contains permitted chemicals
artificial colourings
flavourings
identify pollutants present in water
How to analyse a chromatogram
1.
A single spot
Sample X is a pure substance. It is made up
of one component only.
2.
3 spots
Sample X is a mixture. In this
chromatogram, it shows that it is made up
of three components.
3.
Smudge
Too much sample X is placed on the staring
line. To improve the result, a small and concentrated sample should be placed by using fine capillary tubes. This would ensure that the dyes are clearly separated in distinct lines or spots.
4.
Sample remains
on the starting line
Sample X does not dissolve in the solvent.
A change in the solvent is required.
5.
Different distance
travelled
Components M and N have different
solubility in the same solvent. Component M is more soluble in the
solvent, so it travels faster and covers a
greater distance.
6.
Complete
matching of spots in the
same solvent
Samples X and Y are identical.
7.
Partial matching of spots in the same solvent
Samples X and Y are not identical. Samples X and Y contain two identical
components,
8.
A sample which is made up of other samples
Sample X contains two components of sample Y
and one component of sample Z. Hence, sample X is made by the combinations of samples Y and Z.
Simple distillation
separate a liquid from a solid-liquid mixture.
E.g.
Pure water
separated by seawater
through distillation
Features
Thermometer
Placed near the opening
of the condenser
measure the temperature of the vapour accurately
Distillation flask
Solid-Liquid mixture
Boiling chips
Marble chips
Porcelain chips
smoothen boiling
reducing bumping of liquid
during boiling
prevent overheating
of the liquid being distilled
Anti-bumping
granules
Boiling beads
Boiling stones
Condenser
Liebig Condenser
Water flows
anti-current
to the flow of vapour
Qn: Why does water flow in the opposite direction to the flow of vapour? :question:
Ans: This ensures that the coldest part of the condenser is present before the vapour escapes. Thus, it allows most of the vapour to condense effectively before leaving the apparatus. :check:
Receiving flask
Conical flask
Used as the receiving flask
because
the narrow neck of the flask
reduce the loss
of the distillate through splashing.
A substance is distilled over
temperature remains constant
the boiling point of the substance
Distillate
the liquid collected
from the process
of distillation
A gentle blue flame
used to heat up mixture
in the distillation flask
The distillate is a volatile liquid
receiving flask is placed in a container
filled with ice water
prevent
the distillate from evaporation
A volatile substance
a substance
which evaporates easily
at room temperature
Daily lives
SG
desalinated water is obtained
from seawater
using distillation
seawater is heated
until water changes into steam
condenses in a new container.
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technology of simple distillation
improves the quality of drinking water
in underdeveloped countries
removing impurities
reduces waterborne illnesses
used to extract the natural oils
from
flowers
herbs
for making perfumes
