Separating mixtures


Materials generally mix when two or more of them are put together.

They combine to form a mixture.

A mixture can be between:

  1. a solid and a solid
  2. solids and liquids
  3. liquids and liquids


There are several methods of separating mixtures. The common ones are:

  1. Winnowing

The wind is used to separate wharves (chaff), small sticks, and dry leaves, from grains or seeds by blowing the chaff away.

Chaff is usually lighter than the grains.


2. Sieving

a sieve is used to separate mixtures of particles of different sizes. For example stones from flour.

The larger particles remain on the sieve while the finer ones pass through.


3. Picking

Here the large particles are separated from smaller ones by observing them and using the hands to remove the unwanted ones.

For example, stones are separated from rice or beans in this way.


4. Filtering

This method is used to separate a liquid from particles that cannot dissolve in it.

For example, separating sand from water using filter paper or piece of cloth.


5. Decanting

This is when a liquid is separated from large particles of solids by pouring the liquid out gently.

For example, pouring off kerosene that has mixed with tiny ball bearings.


6. Using a magnet

a magnet is used to separate magnetic materials that may have mixed up with powder or other nonmagnetic materials.

For example, a magnet is used to separate iron filings from sugar.


7. Evaporation

a solid that has dissolved in a liquid is separated in this way. The liquid is heated until it evaporates and the solid is left behind.

For example, salt dissolved in water can be recovered by evaporation.


KCPE Topical Questions

Separating mixtures

1. Which one of the following mixtures is wrongly matched with the method of separating the two substances in their mixture?


Method of separation

A.   Sand and water


B.   Iron and copper

Using a magnet

C.   Coarse sand and fine clay particles


D.   Salt and water



2. Decanting can be used to separate

A. A solid that dissolves in a liquid
B. An insoluble in a liquid
C. Two liquids that can mix
D. Two solids that can mix


3. Which one of the following mixtures can be separated by decanting?

A. Sand and water     B. Sand and sugar
C. Salt and water       D. Salt and iron filings


4. Which one of the following mixtures can be separated by dissolving, filtering and evaporating?

A. Charcoal powder and iron filings
B. Common salt and sand
C. Common salt and sugar
D. Maize flour and iron filings


5. Which one of the following mixtures CANNOT be separated by either dissolving, filtering and evaporating or by using a magnet?

A. Iron fillings and maize flour B. Salt and sugar
C. Salt and sand          D. Iron filings and sand


6. Which one of the following is the most convenient first step in separating a mixture of salt, iron filings, sand, and sawdust?

A. Using a magnet to remove iron filings
B. Using a sieve to remove sand and sawdust
C. Adding water to dissolve the salt
D. Burning to get rid of sawdust

  • Air_winnowing_3 by Unknown used under CC_BY-SA
  • separating by Boquete Panama Guide used under CC_BY-SA
  • Sieving by Eatweeds used under CC_BY-SA
  • Decanting by SOCRATIC used under CC_BY-SA
  • Filtering by onlypicsfine used under CC_BY-SA
  • separating_mixtures_Evaporation by used under CC_BY-SA
  • Using_a_magnet by SupaScience used under CC_BY-SA

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