Quick Revision Notes & Formula Sheet

Class: 6th Science
Chapter: Separation of Substances
Board: MP Board

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### Introduction

We often need to separate harmful or non-useful substances from mixtures. Sometimes, we separate useful components if we need to use them separately.

• Mixture (मिश्रण): A substance containing two or more components mixed together in any proportion.
• Pure Substance (शुद्ध पदार्थ): Contains only one type of particle or component.

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### Key Methods of Separation

1. Handpicking (हाथ से चुनना)

• Definition: The method of separating slightly larger sized impurities like pieces of dirt, stone, and husk from wheat, rice, or pulses by hand.
• Used when: Quantity of mixture is small and impurities are distinct in size, color, or shape.
• Example: Removing stones from rice or lentils.

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2. Threshing (थ्रेशिंग)

• Definition: The process that is used to pull out grain seeds from stalks (straw). Stalks are beaten to free the grain seeds.
• Used when: Harvesting crops like wheat or paddy after they have been dried.
• Example: Beating wheat stalks against a hard surface or using machines (threshers).

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3. Winnowing (निvەی / ओसकना)

• Definition: The method of separating heavier and lighter components of a mixture by wind or blowing air.
• Used when: Lighter husk is mixed with heavier grains.
• Example: Separating wheat grains from husk.

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4. Sieving (चालना)

• Definition: Allows fine flour particles to pass through the holes of the sieve while the bigger impurities remain on the sieve.
• Used when: Components of a mixture have different sizes.
• Example: Separating bran (chokar) from flour, or pebbles and stones from sand at construction sites.

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5. Sedimentation, Decantation, and Loading (अवसादन, निस्तारण और भारायन)

• Sedimentation: When the heavier component in a mixture settles to the bottom after water is added, the process is called sedimentation.
• Decantation: When the water (along with the top layer) is removed, the process is called decantation.
• Loading: Alum (फटकड़ी) is added to water to make suspended muddy particles settle down faster.

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6. Filtration (निसंदन / छानना)

• Definition: The process of separating insoluble solid components from a liquid using a filter (like filter paper or a strainer).
• Example: Separating tea leaves from brewed tea using a strainer.

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7. Evaporation (वाष्पीकरण)

• Definition: The process of conversion of water into its vapor.
• Used when: We want to separate a solid dissolved in a liquid.
• Example: Obtaining common salt from sea water.

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8. Condensation (संघनन)

• Definition: The process of conversion of water vapor into its liquid form.
• Role in separation: Used along with evaporation to obtain both salt and pure water from a saltwater solution (Distillation process).

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### Key Terms to Remember

• Solution (विलयन): A homogeneous mixture of a solute and a solvent (e.g., Salt dissolved in water).
• Solute (विलेय): The substance that gets dissolved (e.g., Salt, Sugar).
• Solvent (विलायक): The liquid in which the solute dissolves (e.g., Water).
• Saturated Solution (संतृप्त विलयन): A solution in which no more substance can be dissolved at that temperature.