Science · Class 6 · Chapter 9

Methods of Separation in Everyday Life

• Mixture — Two or more substances mixed together.
• Handpicking — Sorting by hand.
• Threshing / Winnowing — Separating grain from stalk / husk.
• Sieving — Separating by particle size.
• Sedimentation — Heavier solid settles at the bottom.
• Decantation — Pouring off the liquid on top.
• Filtration — Trapping solids with a porous filter.
• Residue / Filtrate — What's trapped / what passes through.

Chapter 9 · Concept 1 of 9

Handpicking

• Picking out unwanted particles from a mixture by hand — based on differences in size, colour, and shape.
• When it works best — When the unwanted particles are few in number and easy to spot — like picking stones or husk out of grain, or black pepper out of pulao.

Chapter 9 · Concept 2 of 9

Threshing and Winnowing

• Threshing — Separating grains from harvested stalks by beating them — traditionally on a wooden log, or with a threshing machine today.
• Winnowing — Tossing threshed grain into the wind using a soop (bamboo tray) — lighter husk blows away while heavier grains fall close by.

Chapter 9 · Concept 3 of 9

Sieving

• A sieve has holes of a certain size. Fine particles pass through, while larger particles stay on top.
• When to use it — Best when a solid-solid mixture's parts differ in size — like flour and bran, or pebbles and sand at a construction site.

Chapter 9 · Concept 4 of 9

Evaporation: Getting Salt from Seawater

• Seawater is kept in shallow pits exposed to sunlight and air. After some days the water evaporates completely, leaving salt behind.
• Sambhar Lake, Rajasthan — A well-known natural source of common salt made this way — evaporation recovers the salt, but not the water, since it escapes as vapour.

Chapter 9 · Concept 5 of 9

Sedimentation and Decantation

• Sedimentation — A heavier, insoluble part of a mixture settles at the bottom of a liquid — like tea leaves settling in a pan.
• Decantation — Gently tilting the vessel to pour off the liquid above the settled solid — like pouring tea without disturbing the leaves. A few particles may still escape, so it isn't a complete separation on its own.

Chapter 9 · Concept 6 of 9

Filtration

• A porous material — filter paper, cloth, sand, or charcoal — traps solid particles while liquid passes through.
• Residue — The solid trapped on the filter.
• Filtrate — The clear liquid that passes through.

Chapter 9 · Concept 7 of 9

Churning and Magnetic Separation

• Churning — Using a mathni (churner) to separate butter — which floats to the top — from curd, leaving buttermilk behind.
• Magnetic separation — A magnet pulls out magnetic substances like iron nails from non-magnetic ones. Recyclers use large crane-mounted magnets to pull scrap iron from waste heaps.

Chapter 9 · Concept 8 of 9

Why Do We Separate Mixtures?

• To remove the unwanted — Getting rid of one or more components we don't want or can't use — like stones from grain.
• To use both parts — Getting two different useful components separately — like butter and buttermilk from curd. Real mixtures often need several methods applied in sequence.

Chapter 9 · Concept 9 of 9

Methods of Separation, Side by Side

• Method | Basis | Example
• Handpicking — Size, colour, shape — Stones out of grain
• Winnowing — Wind / weight — Husk from grain
• Sieving — Particle size — Flour from bran
• Evaporation — Boiling point — Salt from seawater
• Decantation — Settling + pouring — Tea from tea leaves
• Filtration — Particle size, using a filter — Mud from muddy water

Quick Recap

Check Your Understanding

1. 1What purpose does handpicking serve? (i) Filtration (ii) Sorting (iii) Evaporation (iv) Decantation
2. 2Which method commonly separates cream from milk? (i) Oil from water (ii) Sand from water (iii) Cream from milk (iv) Oxygen from air — by churning
3. 3Which factor is essential for filtration? (i) Apparatus size (ii) Presence of air (iii) Pore size (iv) Temperature of the mixture