StudyNotesHub Class 6 Learning Zone
NCERT Class 6 Science • Chapter 9

Methods of Separation in Everyday Life: Purifying Our World 🌾🥣💧

Discover why and how we separate mixtures! From removing stones from rice to extracting butter from milk, obtaining salt from seawater, and filtering muddy river water, learn all NCERT separation techniques step-by-step.

20 Min Read 4 SVG Diagrams & Experiments 6 Flashcards & 7-Q Quiz

In daily life, most materials around us are mixtures—combinations of two or more substances. We separate components of a mixture for three main reasons:

1. Remove Harmful Impurities 🚫 Removing tiny stones, dirt, or insects from rice, pulses, and wheat before cooking.
2. Separate Non-Useful Components 🍂 Straining tea leaves from prepared tea or husk from harvested grain.
3. Obtain Useful Components 🧈 Churning milk or curd to extract butter, or churning oilseeds for edible oil.

Common Types of Mixtures & Examples:

  • Solid in Solid: Rice and stones, wheat and husk, sand and iron filings.
  • Solid in Liquid (Insoluble): Mud in water, tea leaves in tea, chalk powder in water.
  • Solid in Liquid (Soluble): Salt dissolved in water, sugar dissolved in milk.
  • Liquid in Liquid: Oil floating on water, cream in milk.

1. Handpicking 🖐️

Simple method of picking out visible unwanted impurities by hand when the quantity of mixture is small and impurities differ in size, shape, or color.

📌 When to use: To separate small pieces of stone, husk, or bad grains from wheat, rice, or pulses.

2. Threshing 🌾

Process used to separate grain seeds from harvested stalks. Stalks are beaten against a hard surface (or crushed by bullocks/machines like threshers).

📌 Key Concept: One stalk contains hundreds of grain seeds; handpicking is impossible, so beating is used to free the grains.

3. Winnowing 🌬️

Method used to separate lighter components (husk) from heavier components (grain seeds) of a mixture using blowing wind or air current.

Interactive Diagram: Winnowing Process Blowing Wind ➔ Heavier Grain Heap Lighter Husk Heap

4. Sieving 🧇

Used when components of a mixture have different sizes. Smaller particles pass through the mesh holes of the sieve, while larger impurities remain on top.

🏠 At Home: Fine flour passes through sieve while coarse bran is retained.
🏗️ Construction Sites: Large slanting sieves separate pebbles and stones from sand.

When insoluble solids (like sand or tea leaves) are mixed in water, we use a trio of techniques to purify the liquid:

Step 1

Sedimentation ⏳

The process of allowing heavier insoluble solid particles in a liquid mixture to settle down at the bottom of the container. The settled solid layer is called Sediment.

Step 2

Decantation 🥛

The process of gently pouring off the clear upper liquid layer into another container without disturbing the settled sediment at the bottom.

Step 3 (Perfect)

Filtration ☕

Passing the liquid mixture through a porous medium (like filter paper, cloth, or strainer) to trap fine suspended solid particles. Clear liquid collected is Filtrate.

Interactive Diagram: Sedimentation, Decantation & Filtration Setup 1. Sedimentation Mud Settled 2. Decantation Clear Water 3. Filtration Residue Filtrate

Filtration cannot separate dissolved solids (like salt or sugar) from water because salt particles pass through filter pores. Heat is required instead!

☀️ Evaporation

The process of conversion of a liquid into its vapour form upon heating or exposure to sunlight.

🧂 Obtaining Common Salt from Seawater: Seawater is allowed to stand in shallow pits (Pans). Sunlight heats the water, causing it to evaporate completely into water vapour. White solid common salt remains behind in the pits!

❄️ Condensation

The process of conversion of water vapour back into its liquid form upon cooling.

☕ Kettle Experiment: Steam coming out of a boiling kettle spout condenses into water drops when it touches a cold metal plate holding ice cubes!
Interactive Diagram: Salt Harvesting from Seawater Pits Seawater in Pit Water Evaporates 💨 Solid Salt Left 🧂

Magnetic Separation

Method used to separate magnetic substances (like iron filings, nails, or steel scraps) from a non-magnetic mixture using a magnet or electromagnet.

📌 Everyday Application: Junk yards use massive electromagnets on cranes to lift iron scrap from massive heaps of garbage.

Combining Multiple Methods: Sand + Salt Mixture

How do you separate a mixture of Sand and Salt? A single method is not enough!

  1. Dissolution: Add water to the mixture and stir well. Salt dissolves in water, sand does not.
  2. Decantation / Filtration: Filter the mixture. Insoluble sand remains on filter paper as Residue. Clear salt solution passes through as Filtrate.
  3. Evaporation: Heat the salty filtrate water until all water evaporates, leaving pure salt behind!
🌾

Threshing

Tap to flip 🔄
Process of separating grain seeds from harvested stalks by beating them against a hard surface.
🌬️

Winnowing

Tap to flip 🔄
Separating lighter husk components from heavier grain seeds using blowing air or wind currents.
⏳

Sedimentation

Tap to flip 🔄
Settling down of heavier insoluble solid particles at the bottom of a liquid mixture when allowed to sit undisturbed.
🥛

Decantation

Tap to flip 🔄
Pouring off the clear upper liquid without disturbing the settled sediment particles at the bottom.
☕

Filtration

Tap to flip 🔄
Passing a mixture through a porous filter medium to separate fine insoluble solid particles from a liquid.
☀️

Evaporation

Tap to flip 🔄
Process of converting a liquid into gas/vapour upon heating; used to extract dissolved solids like salt.

Interactive Chapter Quiz 🎯

Test your mastery on methods of separation!

1. Which method is used to separate lighter husk from heavier grain seeds?

2. The process of beating harvested stalks to free grain seeds is known as:

3. Pouring off clear water after heavy mud particles settle down at the bottom is called:

4. Which process is used to obtain common salt from seawater?

5. Converting water vapour back into liquid water droplets upon cooling is called:

6. Which sequence of methods can completely separate a mixture of Sand, Salt, and Water?

7. Which separation method relies on components having different particle sizes?