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Explanation: 1 Mark each
There are various methods used for separating solid particles from substances. Some of them are:
1.Sedimentation
2.Decantation
3.Filtration
Sedimentation: The process of separating insoluble substances which are heavier than liquid by allowing them to settle down on their own due to gravity is called sedimentation. The particles which settle down during sedimentation are called sediments.
Decantation follows sedimentation. In this process, the clear upper liquid is poured out from thecontainer without disturbing the sediment.The upper clear liquid is called supernatant.
Filtrationis a process by whichinsoluble solidscan be removed from a liquid by using afilter paper.

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Definition: 1 Mark
Uses: 1 Mark
Churningis the process of shaking milkin order to convert it tobutter.
It is used to extract butter from milk or curd. It is also used to churn butter from cream.

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Steps: 1 Mark each.
1. Iron nails can be separatedfrom the mixture by handpicking (if the number of iron nails islow) or bymagnetic separation.
2. Tea leaves can be separatedfrom the mixture by filtration.
3. Oil can be separatedfrom the mixture by sedimentation followed by decantation.
4. Salt can be obtained by evaporation of the water.
5. The evaporated water can becondensed and then retrieved.

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Process name: 1 Mark
Explanation: 1 Mark
Evaporation takes place in this case.
Evaporation is a type of vaporization of the liquid that takes place from the surface of a liquid into the gaseous phase.
When the collected water is kept undisturbed in the pot, water is heated by sunlight and slowly turns into water vapour, through evaporation. In few days, the water evaporates completely.
$\therefore$ We do not see any water there after some days.

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Rahulshould use sieving as it will allow the smaller weevils to pass through it while the bigger rice particles will remain on the sieve.

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Explanation: 1 Mark each
1. Amixture of sand and salt is taken in a beaker and water is added to it.
2. After a few seconds of stirring, since saltis soluble in water, the salt will dissolve into the water.
3. The sand being heavier settles at the bottom of the beaker by a process which isknown as sedimentation.
4. The sand can beseparated from the salt solution by decantation or filtration.
5. The remaining mixture of salt and water is heated and the waterevaporates to form water vapour.
6. Now, onlysalt is left into the beaker and the water vapour can be converted back into water through condensation.

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Filtration iscommonly defined as the mechanical or physical operation used to separate insoluble solid particlesfrom solid-liquid mixturedue to the difference in the size of solid-liquid particles.
So, the most appropriate method of removing tea leaves after preparing tea is by filtration.
A tea strainer can be used to fulfill the above separation process.The smaller size of holes of the tea strainer does not allow solid particles to pass through them, but the liquid passes through it.

Answer: Option B. -> Sieve
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B
Sieves are used to separate gravel from sand. Sieving is a simple technique for separating particles of different sizes. Depending upon the types of particles to be separated, sieves with different sizes of holes are used.

Answer: Option B. -> Filtration 
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B
Filtration is a method forseparating an insoluble solid from a liquid.
For example: When a mixture of sand and water is filtered, the sand stays in the filter paper (residue) while the water passes through the filter paper and gets collected below.

Answer: Option C. -> evaporation
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C
Seawater contains large amounts of common salt. Near the sea-shore, the seawater is collected in shallow pits. In a few days, the water evaporates by absorbing heat from sunrays, leaving behind the salt. This salt is collected and further processed and purified.