A brief presentation on mixing and separation of substances.

1. CLASS-1
SEPARATION OF SUBSTANCES
Dr. Madhava B Mallia
Navi Mumbai Science Foundation
Guidance session for Homi Bhabha Bal Vaidnyanik Competition
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2. We are going to see…
• Why we need to separate substances in a mixture
• What are mixtures
• Different type of mixtures
• Methods of separation of mixtures
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3. A look at our daily life…
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4. Would you like to use
these as such?
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5. Noooooooooo………..Why?
• Because it is IMPURE….
• So what is PURE?
PURE means made up of only one type of matter or substance
Impure Pure Impure Pure
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6. Why substances become impure?
• Because they mix with other substances
Lets learn about mixtures….
• States of matter
1. Solid
2. Liquid
3. Gas
4. Plasma  we will not consider it for the time being
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7. Lets look at different ways of mixing…
MIXTURES OF SOLID
LARGER AMOUNT SMALLER AMOUNT Examples
SOLID SOLID Stones in rice, Rice hulls in rice, fruit-salad
SOLID LIQUID Mud, concrete
SOLID GAS Hydrogen gas on palladium metal
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8. MIXTURES OF LIQUID
LARGER AMOUNT SMALLER AMOUNT Examples
LIQUID SOLID Muddy water, mercury amalgum (metal dissolved in mecury)
LIQUID LIQUID Vinegar (acetic acid in water)
LIQUID GAS Air dissolved in water, Soda
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9. MIXTURES OF GAS
LARGER AMOUNT SMALLER AMOUNT Examples
GAS SOLID Smoke, Dust
Smoke – soot/carbon suspended in air
Dust – fine sand particles suspended in air
GAS LIQUID Water vapour
GAS GAS Air
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10. Types of mixtures
• Homogeneous mixtures
• Heterogeneous mixtures
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11. Homogeneous mixtures
A B C D
1. Take a glass of water
2. Add a spoon of salt
3. Mix it well
4. What is your observation?
The salt dissolves completely
What we get is a mixture?
Yes, a liquid-solid mixture
Now lets distribute this mixture into
four small cups A, B, C & D
Taste from each cup…
Does it taste the same?
Yes, This is because the salt
we added was distributed
uniformly in water
A uniform mixture is called homogeneous mixture or SOLUTION

12. Examples of homogeneous mixtures or solutions
• Alloys – Alloys are homogeneous mixture of two or more metals
Brass – an alloy of copper and zin
Bronze – an alloy of copper, tin and small amounts of other metals
• Fruit juices without pulp
• Sugar dissolved in water
• Air – mixture of 78.09% nitrogen, 20.95% oxygen, 0.93% argon, 0.04%
carbon dioxide, and small amounts of other gases.
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13. Heterogeneous mixtures
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A B C
Will each plate A, B and C contain same amount
of different fruits?
No….different plates contain fruits in different
amount
A non-uniform mixture is called heterogeneous mixture

14. Non-mixing substances
• Certain substances do not mix with each other
– Oil and water
– Wax and water
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15. Would you like to use
these as such?
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16. Methods of separation
• Hand picking
• When will we use this method?
– Impurity to be separated is larger in size
– Impurity to be separated is smaller in quantity
Example:
Separation of stones, hull, other grains etc. from rice
WILL YOU USE HAND PICKING IF RICE IS MIXED WITH SAND?
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17. • Threshing
• When will we use this method?
– material to be separated is loosely bound
– material to be separated is too larger in quantity for hand picking
Examples:
Separation of grains from stalk
Removal of dirt from cloths
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Methods of separation

18. • Winnowing
• When will we use this method?
– When the impurity to be separated is much lighter for the wind to
carry it away
Examples:
Separation of husk from grains
Separation of peanut peals
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Methods of separation

19. • Sieving
• When will we use this method?
– Impurities are bigger in size than the material to be purified
Examples:
Separation of stones and insects from flour
Separation of stones and pebbles from sand
HAND PICKING IS POSSIBLE HERE, BUT IT WILL BE TIME CONSUMING
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Methods of separation

20. • Sedimentation followed by decantation
• When will we use this method?
– Separation of heavier impurities in liquids
– Separation of lighter impurities in solids
Examples:
Separation of sand from water
Separation of husk from rice
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Methods of separation

21. 21
Decantation

22. • Filtration
• When will we use this method?
– When decantation is not satisfactory!!
Examples:
Separation of tea leaves from tea
Separation of home-made paneer
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Methods of separation

23. • Evaporation
• Evaporation is the process by which water changes from liquid
state to vapor.
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Methods of separation

24. • When will we use this method?
– When we have to recover substances dissolved in water
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Evaporation
SALT
Salt farm or salt pan

25. How will you separate salt mixed with sand?
(Using combination of methods)
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SALT SAND
• Dissolve salt + sand mixture in water
 Salt will dissolve in water
• Allow the mixture to stand for some time
 Sand will settle down (sedimentation)
• Separate sand from salt water (decantation or filtration)
• Evaporate salt water to recover salt (Evaporation)
WHAT IF WE WANT TO COLLECT WATER ALSO?

26. Condensation
• Condensation is the process of conversion of vapors into liquid
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Water
evaporating
to
Atmosphere
Salt water So we have to cool the vapors to condense it
How to recover
evaporating
water?

27. 27
Water
evaporating
to
Atmosphere
Natural
evaporation
is very slow
VERY DIFFICULT TO CONDENCE VAPOURS
ice

28. • Magnetic separation
• When will we use this method?
– Either substance to be purified or the impurity is magnetic
Example:
Separation of iron filings from sand
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Methods of separation

29. Separation of a mixture of salt, sand and iron filings
• Step 1: Separate iron filings using a magnet
• Step 2: Add the remaining mixture to water
• Step 3: Decant/filter off sand
• Step 4: Evaporate the solution to recover salt
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30. Industrial methods of separation
• Industrial scale  large scale
• Methods
– Centrifugation
– Distillation
– Magnetic separation
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31. • Centrifugation
It is a technique that uses centrifugal force to separate
substances
Example:
Quick separation of sand and water (muddy water)
Separation of red bloods cells, white blood cells etc. from blood
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Industrial methods of separation

32. 32
Centripetal force
Towards the centre
Centrifugal force
Away from the centre
If the string breaks…..the stone will
move away from the centre

33. 33
Centrifugal
force on
mud/sand
particles
Blood before and after
centrifugation
There is a centrifuge in most of your homes – can you identify?

34. 34
WASHING MACHINE

35. • Distillation
• Method used to separate two liquids which boil at different
temperatures
Example:
Distillation of salt water to obtain pure water
Distillation of ethanol from water
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Industrial methods of separation
Substance Boiling point
Salt Very very high
Ethanol 78.3 degree centigrade
Water 100 C

36. Simple distillation apparatus
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37. • Petroleum products from crude oil
– Petrol, diesel, aviation turbine oil, tar…
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38. • Magnetic separation
• When will we use this method?
– When material to be separated or the impurity is magnetic
Example:
Separation of metals in recycling centers
Separation of ore from sand and other impurities
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Industrial methods of separation

39. Iron ore separator
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Iron ore
Feeder

40. Properties of material Vs Method of separation
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Size/Shape Weakly bound
substances/impurities
Weight
(light/heavy)
Density
(mass per unit volume)
Volatility
(tendency to evaporate
under normal
conditions)
Magnetic property
Hand picking
Threshing
Winnowing
Sieving
Sedimentation
Decantation
Filtration
Evaporation
Condensation
Centrifugation
Distillation
Magnetic separation

41. Separation based on shape
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42. Saturated solution
• A solution in which we cannot dissolve a substance any further
is called a saturated solution
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Unsaturated solution Unsaturated solution saturated solution

43. 43
Substance Solubility in 500 mL of water at 25 degree centigrade
Baking soda
(Sodium bicarbonate)
48 gram
Table salt 180 gram
Sugar 1000 gram