Class 6 Science Chapter 9 Methods of Separation in Everyday Life Notes & Summary in English for CBSE students
CBSE Class 6 Science Chapter 9 Notes & Summary in English for “Methods of Separation in Everyday Life” (based on NCERT textbook Curiosity ).
Chapter 9 – Methods of Separation in Everyday Life Complete Notes
(Complete Notes + Concept-wise Explanation + Summary CBSE Class 6 Science – Curiosity Book)
1. Why Do We Need to Separate Substances?
In our daily lives, different substances are often mixed together.
Some components are useful, while others are harmful or unwanted.
To make a mixture safe or suitable for use, we separate its components.
Examples
• Removing stones from rice and dal before cooking
• Separating tea leaves from tea
• Separating butter from curd
• Obtaining salt from seawater
Two main reasons for separation:
- To remove harmful or unwanted substances
- To separate two useful components
2. Handpicking
Handpicking is used when:
• The unwanted materials are in small quantity
• The size, colour or shape of unwanted items is different from useful ones
• The particles are large enough to be picked by hand
Examples
• Removing stones from rice or wheat
• Removing spoiled grains
• Picking black pepper from food
Key point: Handpicking works only when the impurities are few and large enough to be picked manually.
3. Threshing
Threshing is the process of separating grains from stalks.
Farmers beat the harvested stalks on a hard surface so that grains come out.
Why threshing is needed
Grains grow attached to stalks. They must be separated before further cleaning.
Traditional method
• Farmers beat the stalks manually.
Modern method
• Thresher machines perform threshing and winnowing together.
4. Winnowing
Winnowing separates heavier and lighter components with the help of wind.
How it works
• The mixture is dropped from a height in the direction of wind.
• The heavier component (grains) falls straight down.
• The lighter component (husk) gets blown away.
Examples
• Separating husk from wheat or rice
• Separating peanut skin from peanuts
Key idea
Winnowing works due to differences in weight.
5. Sieving
Sieving is used when components of a solid–solid mixture have different sizes.
How it works
• A sieve has many tiny holes of the same size.
• Smaller particles pass through the holes.
• Larger particles remain on the sieve.
Examples
• Separating bran from flour
• Separating small stones from sand at construction sites
• Separating coconut pieces from fine rice flour
Important point
Sieving works only when particle size difference is significant.
6. Evaporation
Evaporation is the process in which a liquid changes into vapour.
When is evaporation used for separation?
• When a solid is dissolved in a liquid
• To recover the solid but not the liquid
Examples
• Obtaining salt from seawater
• Getting salt back from salt solution
• Drying medicines (Ayurveda)
How it works
• Seawater is left in shallow pits.
• Sunlight and wind evaporate the water.
• Salt remains behind as the solid component.
Note
Evaporation does not give back water.
7. Sedimentation and Decantation
Sedimentation
• Heavier insoluble particles settle at the bottom of a liquid.
• After waiting for some time, the mixture separates into two layers.
Decantation
• The clean water at the top is gently poured out.
Important points
• Used when particles are heavy.
• Used in cleaning pulses or rice before cooking.
• Used to separate oil and water (because oil floats on top).
8. Filtration
Filtration separates insoluble solids from liquids.
How filtration works
• A filter (cloth, strainer, filter paper) has tiny pores.
• Water passes through, leaving solid particles behind.
Examples
• Separating tea leaves from tea
• Filtering muddy water using cloth or filter paper
• Filtering pond water in a homemade filter
Residue: The solid left on the filter
Filtrate: The clear liquid that passes through
Materials that can act as filters
• Cloth
• Charcoal
• Cotton
• Sand
• Filter paper
9. Churning
Churning is used to separate lighter solids from heavier liquids.
How it works
• When curd is churned using a mathni or mixer, butter separates from buttermilk.
• Butter floats because it is lighter.
Examples
• Butter from curd
• Ghee from butter (after heating)
10. Magnetic Separation
Some substances get attracted to magnets.
This method separates magnetic materials from non-magnetic materials.
Examples
• Iron nails in sawdust
• Iron scrap from garbage heaps
• Iron filings from sand
Magnetic substances
• Iron
• Nickel
• Cobalt
11. Combining Methods of Separation
Sometimes, more than one method is needed.
Example
A mixture of salt, sand, and iron filings requires:
- Magnetic separation to remove iron
- Filtration to remove sand
- Evaporation to obtain salt from water
Important idea
The order of steps depends on properties of substances.
12. Understanding Real-Life Applications
Mixtures we commonly separate
• Muddy water
• Salt solution
• Grains and husk
• Tea and tea leaves
• Oil and water
• Pebbles from sand
Why masks work (chapter link)
• Masks block dust and dirt through tiny pores (similar to filtration).
Why fishnets work
• Nets act like filters, letting water pass and trapping fish.
White patches on clothes in summer
• Salt from sweat remains after water evaporates (example of evaporation).
Important Activities Explained
Activity 9.1: Peanut Skin Separation
- Rubbing peanuts removes skin
- Blowing air carries away the lighter skin
- Demonstrates: winnowing
Activity 9.2: Salt Solution Evaporation
- Salt dissolves completely in water
- After drying, salt remains as patches
- Water evaporates
Activity 9.3: Heating Salt Solution
- Water boils away
- Salt remains in china dish
- Demonstrates evaporation
Activity 9.4: Filtration Using Filter Paper
- Muddy water filtered using folded filter paper
- Mud stays on paper
- Clear water collects below
Frequently Confused Concepts
Evaporation vs Filtration
- Evaporation: separates dissolved solids
- Filtration: separates insoluble solids
Sedimentation vs Decantation
- Sedimentation: settling
- Decantation: pouring out clear liquid
Winnowing vs Sieving
- Winnowing: differences in weight
- Sieving: differences in size
Handpicking vs Threshing
- Handpicking: remove small impurities manually
- Threshing: remove grains from stalks
Summary of All Key Methods
Below is a simple summary table of all methods:
| Method | Used For | Example |
|---|---|---|
| Handpicking | Large, easily visible impurities | Stones from rice |
| Threshing | Separating grains from stalks | Wheat, paddy |
| Winnowing | Separating lighter and heavier components | Husk from grains |
| Sieving | Different-sized solid particles | Bran from flour |
| Evaporation | Recovering solid from solution | Salt from seawater |
| Sedimentation | Heavy solids settling | Mud in water |
| Decantation | Removing clear liquid from above | Oil from water |
| Filtration | Insoluble solids from liquids | Tea leaves from tea |
| Churning | Separating lighter solids from liquids | Butter from curd |
| Magnetic Separation | Magnetic from non-magnetic | Iron from sawdust |
Chapter Summary – key points
• We often need to separate mixtures to remove impurities or obtain useful substances.
• Different methods are chosen based on particle size, weight, solubility, and magnetic properties.
• Handpicking, threshing, winnowing, sieving, evaporation, sedimentation, decantation, filtration, churning, and magnetic separation are the major methods.
• Some mixtures require a combination of several methods.
• Separation processes are widely used in agriculture, homes, industries, and nature.
• Understanding the properties of substances helps in choosing the correct method of separation.