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Methods of Separation of Substances - Sedimentation, Decantation, and Filtration

Grade 6CBSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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Sedimentation: This process occurs when the heavier, insoluble component in a mixture settles at the bottom after adding water. It is primarily used for separating solid particles that do not dissolve in a liquid.

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Decantation: Once sedimentation is complete, the liquid above the sediment is poured out into another container without disturbing the settled particles. This process is called decantation and is also used to separate two immiscible liquids like oil and H2OH_2O.

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Filtration: This is the process of passing a mixture through a filter (like filter paper, a fine cloth, or a strainer) to separate solid particles from a liquid. The solid trapped on the filter is called the 'residue', and the liquid that passes through is called the 'filtrate'.

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Insoluble Solids: These methods are specifically used for mixtures where the solid component is insoluble in the liquid (e.g., sand in H2OH_2O or tea leaves in tea).

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Loading: Sometimes, very fine suspended particles in H2OH_2O (like clay) take a long time to settle. Adding substances like Alum (KAl(SO4)2⋅12H2OKAl(SO_4)_2 \cdot 12H_2O) speeds up sedimentation by making the particles heavier.

📐Formulae

Mixture=Solute (Insoluble)+Solvent (Liquid)\text{Mixture} = \text{Solute (Insoluble)} + \text{Solvent (Liquid)}

Rate of Sedimentation∝Mass of Particles\text{Rate of Sedimentation} \propto \text{Mass of Particles}

Total Mass=mresidue+mfiltrate\text{Total Mass} = m_{\text{residue}} + m_{\text{filtrate}}

💡Examples

Problem 1:

How can you separate a mixture of sand and water (H2OH_2O) using the methods discussed?

Solution:

Use a combination of Sedimentation and Decantation.

Explanation:

Leave the mixture undisturbed for some time. The heavy sand particles will settle at the bottom (Sedimentation). Then, carefully tilt the container to pour the clear water into another beaker (Decantation).

Problem 2:

Which method is more effective for removing fine mud particles from water: Decantation or Filtration?

Solution:

Filtration is more effective.

Explanation:

In Decantation, some fine particles might still remain suspended or get poured out with the liquid. Filtration using a filter paper with tiny pores ensures that even the smallest insoluble mud particles are trapped as residue, providing a clearer filtrate of H2OH_2O.

Problem 3:

How would you separate a mixture of mustard oil and water (H2OH_2O)?

Solution:

Decantation.

Explanation:

Since oil and H2OH_2O are immiscible (they do not mix) and oil is lighter than water, oil forms the top layer. By tilting the container, the top layer of oil can be poured off, leaving the H2OH_2O behind.