class 6 ncert science separation of substances chapter 5

1. NIDHI KAUSHIK
CLASS- 6
CHAPTER 5

2. THE NEED FOR SEPARATION OF SUBSTANCES
TO SEPARATE TWO DISSIMILAR BUT USEFUL ELEMENTS
LIKE IN THE CASE OF BUTTER AND MILK. MILK IS CHURNED
IN ORDER TO OBTAIN BUTTER.
TO SEGREGATE USELESS ELEMENTS FROM THE USEFUL
ONES LIKE IN THE CASE OF SEPARATING TEA LEAVES
FROM TEA.
TO REMOVE AND DISCARD IMPURITIES OR POTENTIALLY
HARMFUL SUBSTANCES LIKE PICKING OUT SMALL PIECES
OF STONES AND OTHER IMPURITIES FROM RICE AND
WHEAT.

3. SCIENCECLASS
PROBLEMS ARISE WHEN THE MATERIALS
TO BE SEPARATED ARE REALLY SMALL IN
SIZE OR DIFFER IN THEIR COMPOSITION.
IT IS NEARLY IMPOSSIBLE TO SEPARATE
GRAINS OF SALT FROM GRAINS OF SAND
BY HAND OR TRYING TO SEPARATE OIL
FROM WATER.
WE MIGHT NEED TO USE METHODS
OTHER THAN SIMPLE HANDPICKING EVEN
THOUGH FOR A LOT OF SEPARATION
PROCESSES, EVEN HANDPICKING MIGHT
BE ENOUGH.

4. PRINCIPLE OF SEPARATION
THE SUBSTANCES PRESENT IN A
MIXTURE RETAIN THEIR ORIGINAL
PROPERTIES LIKE PARTICLE SIZE,
DENSITY, MELTING POINT, BOILING
POINT, VOLATILITY, ETC.
WE USE THE DIFFERENCE IN ANY ONE
OF THESE PROPERTIES IN THE
COMPONENTS OF A MIXTURE TO
SEPARATE THEM.

5. SEPARATION OF SOLID
SUBSTANCES FROM THE
MIXTURESHANDPICKING,
WINNOWING,
SIEVING,
THRESHING

6. THESIMPLEPROCESSOFSEPARATING
SLIGHTLYBIGGERSIZEDHARMFUL
SUBSTANCESOROTHERUSEFULSUBSTANCES
ORIMPURITIESLIKESMALLPIECESOFSTONES,
HUSKANDDIRTFROMGRAINSOFWHEAT,
PULSESANDRICEISCALLEDHANDPICKING.
I
NSITUATIONSWHENTHEQUANTITYOFSUCH
IMPURITIESISNOTVERYLARGE,HANDPICKING
TURNSOUTTOBEATIME-SAVINGAND
CONVENIENTPROCEDUREOFSEPARATING
SUBSTANCES.
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7. Threshing:

8. WINNOWING

9. SIEVING:SOMETIMESEVENAFTERTHEGRAINSEEDSHAVE
PASSEDTHROUGHTHESTAGESOFTHRESHINGAND
WINNOWING,HUSKMAYSTILLBEATTACHEDTOTHEGRAINOR
ITMAYHAVECOLLECTEDSTONESANDDIRTINTHEEARLIER
STAGESWHICHNEEDTOBEREMOVEDANDTHISSEPARATION
ISUSUALLYDONEWITHTHEHELPOFASIEVE.
SIEVINGISAVERYSIMPLE,CONVENIENTANDTIME-SAVING
PROCESSTHROUGHWHICHPARTICLESOFVARYINGSIZESCAN
BESEPARATEDFROMEACHOTHERWITHTHEHELPOFASIEVE.
ASIEVEISNOTHINGBUTASIMPLEDEVICEWITHSMALLPORES
INITWHICHALLOWFINERMATERIALSLIKEFLOURTOPASS
THROUGHLEAVINGBEHINDANYIMPURITIESITMIGHTCONTAIN.
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10. SEPARATION OF INSOLUBLE
SOLIDS FROM A LIQUID
SEDIMENTATION,
DECANTATION,
LOADING,
FILTRATION

11. SEDIMENTATION CAN BE DEFINED AS
THE PROCESS THROUGH WHICH DIRT
AND OTHER HEAVIER PARTICLES IN A
MIXTURE SETTLE AT THE BOTTOM OF
THE VESSEL WHEN WATER IS ADDED
TO IT. WHEN THE DUST AND DIRT
PARTICLES HAVE SETTLED, THE CLEAR
WATER WHICH FORMS THE UPPER
LAYER IS MOVED TO A DIFFERENT
CONTAINER AND THE DIRT AND DUST
IS DONE AWAY WITH. THIS TECHNIQUE
CAN ALSO BE USED TO SEPARATE TWO
LIQUIDS WHICH DO NOT MIX WITH
EACH OTHER (ALSO CALLED IMMISCIBLE
LIQUIDS) AND IS CALLED
DECANTATION.
S
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12. D
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DECANTATION CAN BE DEFINED AS A
TECHNIQUE THROUGH WHICH IMMISCIBLE
LIQUIDS OR A LIQUID AND A SOLID
SUBSTANCE ARE SEPARATED. FOR EXAMPLE,
TAKE THE CASE OF OIL AND WATER. THESE
ARE TWO EXAMPLES OF IMMISCIBLE
LIQUIDS. ONCE WE POUR OIL IN WATER, OIL
FORMS THE UPPER LAYER OF WATER AND
CAN BE EASILY SEPARATED BY GENTLY
POURING THE MIXTURE IN ANOTHER
CONTAINER TILL ALL THE OIL HAS BEEN
REMOVED. SOMETIMES SMALLER DIRT
PARTICLES GET CARRIED ALONG WITH THE
WATER IN THE PROCESS OF DECANTATION
WHICH NEEDS TO BE FURTHER REMOVED.
THIS CAN BE ACHIEVED THROUGH THE
PROCESS OF FILTRATION.

13. F
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FILTRATION IS THE PROCESS THROUGH
WHICH SMALLER PARTICLES LIKE DIRT ETC.
ARE SEPARATED FROM A SOLUTION BY
MAKING THE SOLUTION PASS THROUGH A
MEDIUM (OFTEN A FILTER PAPER). THIS
MEDIUM IS SUCH THAT ONLY LIQUIDS ARE
ABLE TO PASS THROUGH IT BECAUSE OF THE
PRESENCE OF VERY TINY PORES IN IT.
THE FILTER PAPER IS MOLDED TO FORM A
CONE AND THIS CONE-LIKE STRUCTURE IS
THEN AFFIXED TO A FUNNEL THROUGH
WHICH THE DIRTY SOLUTION IS ALLOWED TO
PASS. SOMETIMES, FILTRATION CAN ALSO BE
APPLIED TO SEPARATE PULP AND SEEDS
FROM THE JUICE. IT CAN ALSO BE USED TO
SEPARATE COTTAGE CHEESE OR PANEER
FROM MILK.

14. SEPARATION OF SOLUBLE
SOLIDS FROM A MIXTURE
EVAPORATION

15. EVAPORATION IS THE PROCESS OF CONVERTING LIQUID INTO
GAS OR VAPOUR BY INCREASING THE TEMPERATURE OR
PRESSURE OF THE LIQUID. THIS PROCESS IS OFTEN USED TO
SEPARATE SALT FROM SALT WATER OR SALTY SEA WATER. SEA
WATER HAS A NUMBER OF SALTS PRESENT IN IT. SHALLOW
PITS CALLED EVAPORATION PONDS ARE CONSTRUCTED AND
SALT WATER IS ALLOWED TO STAND IN THESE. AFTER SOME
TIME, THE WATER GETS EVAPORATED, LEAVING BEHIND THE
SALTS. COMMON SALT IS SEPARATED FROM THIS MIXTURE
UPON FURTHER PURIFICATION.
Evaporation:

16. SEPARATION OF LIQUID
FROM A MIXTURE
CONDENSATION,
DISTILLATION

17. THE SIMPLE PROCESS OF
CONVERTING GAS OR
VAPOUR TO ITS LIQUID
FORM BY DECREASING
THE TEMPERATURE OR
PRESSURE EXERTED ON
IT.
CONDENSATION

18. DISTILLATION
DISTILLATION IS THE
PROCESS OF SEPARATING
THE COMPONENTS OR
SUBSTANCES FROM A
LIQUID MIXTURE BY
USING SELECTIVE BOILING
AND CONDENSATION

19. SEPARATION OF IMMISCIBLE
LIQUID FROM A MIXTURE
SEPARATING FUNNEL,

20. A separatory funnel

21. SOLUTION AND SOLUBILITY:

22. EVEN THOUGH WATER CAN DISSOLVE A NUMBER OF SUBSTANCES AND
SOLUTIONS IN IT, IT HAS A LIMIT TO HOW MUCH IT CAN DISSOLVE. AFTER A
CERTAIN POINT, IT STOPS DISSOLVING ANY MORE OF THAT SUBSTANCE AND
THE SUBSTANCE COLLECTS AT THE BOTTOM OF THE VESSEL. WE SAY THAT
THE SOLUTION HAS BECOME SATURATED.
A SATURATED SOLUTION IS ONE THAT CONTAINS THE MAXIMUM POSSIBLE
CONCENTRATION OF A PARTICULAR SOLUTE.
A SOLUTE IS DEFINED AS A VERY SMALL ELEMENT IN A SOLUTION THAT IS
DISSOLVED IN A SOLUTION.
ONE WAY OF ENSURING THAT THE GIVEN AMOUNT OF WATER TAKES MORE
SALT EVEN AFTER IT HAS REACHED ITS SATURATION POINT IS BY HEATING
THE SAID WATER. THIS IS BECAUSE HEATING THE SOLUTION HELPS TO
INCREASE THE SOLUBILITY OF SALT OR ANY SOLUTE AND HENCE MORE
AMOUNT OF THE SAME SOLUTE CAN NOW BE DISSOLVED IN THE SAME
AMOUNT OF WATER.

23. THE SUBSTANCE THAT DISSOLVES IS
CALLED THE SOLUTE AND THE
SUBSTANCE IN WHICH THE SOLUTE
DISSOLVES IS CALLED THE SOLVENT.
THE RESULTING MIXTURE IS CALLED
THE SOLUTION. THUS, SOLUTE +
SOLVENT = SOLUTION.
E.G., SUGAR + WATER = SUGAR
SOLUTION.

24. CHURNING: THE PROCESS OF SHAKING MILK OR CREAM IN
ORDER TO ALLOW LIGHTER PARTICLES TO COME TO THE
SURFACE IN ORDER TO MAKE BUTTER IS CALLED
CHURNING.
PURE SUBSTANCE: THIS CAN BE DEFINED AS A SUBSTANCE
COMPOSED OF ONLY A SINGLE TYPE OF PARTICLE.
IMPURE SUBSTANCE: A SUBSTANCE COMPOSED OF MORE
THAN ONE TYPE OF PARTICLES.
SUBLIMATION: WHEN A SOLID DIRECTLY GETS
CONVERTED INTO VAPOUR, THIS PROCESS IS KNOWN AS
SUBLIMATION.
MAGNETIC SEPARATION: THIS IS ANOTHER METHOD OF
SEPARATION WHICH ALLOWS METALS (AND OTHER
ARTICLES WHICH ARE ATTRACTED TO A MAGNET) TO BE
SEPARATED FROM A MIXTURE WITH THE HELP OF A
MAGNETIC OR BY APPLYING A MAGNETIC FORCE TO IT.
FOR EXAMPLE, A MIXTURE OF SALT AND IRON FILINGS CAN
BE SEPARATED WITH THE HELP OF A MAGNET.
Some
Important
Definitions

25. 1. WHY DO WE NEED TO
SEPARATE DIFFERENT
COMPONENTS OF A MIXTURE?
GIVE TWO EXAMPLES.
SOLUTION:
WHEN TWO OR MORE
SUBSTANCES ARE MIXED
TOGETHER THEY FORM A
MIXTURE. COMPONENTS OF A
MIXTURE SHOULD BE
SEPARATED BECAUSE SOME
COMPONENTS MAY NOT BE
USEFUL OR MAY SPOIL THE
USEFUL COMPONENT OF THE
MIXTURE.
SCIENCECLASS
2. WHAT IS WINNOWING?
WHERE IS IT USED?
SOLUTION:
THE METHOD OF
SEPARATING THE
COMPONENTS FROM A
MIXTURE. IN THIS METHOD,
HEAVIER AND LIGHTER
COMPONENTS OF A MIXTURE
ARE SEPARATED BY WIND OR
BY BLOWING AIR. THIS
METHOD IS USED TO
SEPARATE GRAINS FROM
HUSK.
NCERT
EXERCISE

26. SCIENCECLASS
3. HOW WILL YOU
SEPARATE HUSK OR
DIRT PARTICLES FROM A
GIVEN SAMPLE OF
PULSES BEFORE
COOKING?
SOLUTION:
HUSK AND DIRT
PARTICLES ARE
SEPARATED FROM
PULSES BY
HANDPICKING.
4. WHAT IS SIEVING?
WHERE IS IT USED?
SOLUTION:
SIEVING IS A METHOD IN
WHICH FINE PARTICLES
ARE SIEVED THROUGH
HOLES OF THE SIEVE
WHILE THE BIGGER
IMPURITIES REMAIN ON
THE SIEVE. SIEVING IS
USED IN A FLOUR MILL TO
SEPARATE IMPURITIES
LIKE HUSK AND STONES
FROM WHEAT BEFORE
GRINDING IT.

27. SCIENCECLASS
5. HOW WILL YOU SEPARATE
SAND AND WATER FROM THEIR
MIXTURE?
SOLUTION:
SAND AND WATER ARE
SEPARATED FROM THEIR
MIXTURE BY THE FOLLOWING
STEPS:
A) THE MIXTURE IS ALLOWED TO
STAND WITHOUT ANY
DISTURBANCES
B) NOW SAND SETTLES DOWN
C) SLOWLY POUR THE WATER
INTO ANOTHER CONTAINER TO
OBTAIN SAND IN THE BOTTOM
6. IS IT POSSIBLE TO SEPARATE
SUGAR MIXED WITH WHEAT
FLOUR? IF YES, HOW WILL YOU DO
IT?
SOLUTION:
YES IT IS POSSIBLE TO SEPARATE
SUGAR MIXED WITH WHEAT
FLOUR BY THE FOLLOWING
METHOD
A) MIX SUGAR AND WHEAT FLOUR
IN WATER
B) STIR THE SOLUTION TO ALLOW
SUGAR TO DISSOLVE
C) NOW FILTER THE MIXTURE
D) FILTRATE CONTAINS SUGAR
SOLUTION AND RESIDUE WILL BE
WHEAT FLOUR.

28. SCIENCECLASS
7. HOW WOULD YOU
OBTAIN CLEAR WATER
FROM A SAMPLE OF
MUDDY WATER?
SOLUTION:THE
FOLLOWING PROCESS
SHOULD BE CARRIED OUT
TO OBTAIN CLEAR
WATER FROM MUDDY
WATERI) ALLOW MUDDY
WATER TO STANDII)
MUD GETS SETTLED
DOWN IN THE WATERII)
SLOWLY POUR WATER TO
ANOTHER CONTAINER
8. FILL UP THE BLANKS
(A) THE METHOD OF SEPARATING SEEDS
OF PADDY FROM ITS STALKS IS CALLED
___________.
(B) WHEN MILK, COOLED AFTER BOILING,
IS POURED ONTO A PIECE OF CLOTH THE
CREAM (MALAI) IS LEFT BEHIND ON IT.
THIS PROCESS OF SEPARATING CREAM
FROM MILK IS AN EXAMPLE OF
___________.
(C) SALT IS OBTAINED FROM SEAWATER
BY THE PROCESS OF ___________.
(D) IMPURITIES SETTLED AT THE BOTTOM
WHEN MUDDY WATER WAS KEPT
OVERNIGHT IN A BUCKET. THE CLEAR
WATER WAS THEN POURED OFF FROM
THE TOP. THE PROCESS OF SEPARATION
USED IN THIS EXAMPLE IS CALLED
___________.
THRESHING.
FILTRATION.
EVAPORATION.
DECANTATION.

29. SCIENCECLASS
9. TRUE OR FALSE?
(A) A MIXTURE OF MILK AND WATER CAN BE
SEPARATED BY FILTRATION.
(B) A MIXTURE OF POWDERED SALT AND
SUGAR CAN BE SEPARATED BY THE PROCESS
OF WINNOWING
(C) SEPARATION OF SUGAR FROM TEA CAN BE
DONE WITH FILTRATION.
(D) GRAIN AND HUSK CAN BE SEPARATED
WITH THE PROCESS OF DECANTATION.
SOLUTION:
A) FALSE
B) FALSE
C) FALSE
D) FALSE
10. LEMONADE IS
PREPARED BY MIXING
LEMON JUICE AND SUGAR
IN WATER. YOU WISH TO
ADD ICE TO COOL IT.
SHOULD YOU ADD ICE TO
THE LEMONADE BEFORE
OR AFTER DISSOLVING
SUGAR? IN WHICH CASE
WOULD IT BE POSSIBLE TO
DISSOLVE MORE SUGAR?
SOLUTION:
ICE SHOULD BE ADDED TO
SUGAR AFTER
DISSOLVING SUGAR. IT IS
POSSIBLE TO ADD MORE
SUGAR BEFORE ADDING
ICE.

30. This Photo by Unknown Author is licensed under CC BY-NC-ND