Quick Revision Notes: Class 6 Science

Chapter: Sorting Materials into Groups

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1. Introduction to Matter and Materials

• Object: Anything that we can see, touch, and is made up of some matter.
• Material: The substance used to make different objects is called a material (e.g., wood, plastic, glass, metal).
• Grouping (Classification): Sorting objects or materials into groups based on similarities and differences in their properties.

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2. Why Do We Need to Group Materials?

• Convenience: It helps us easily locate and access objects.
• Understanding Patterns: It helps us study and observe patterns in the properties of objects.
• Efficiency: Making use of materials becomes organized (e.g., in a grocery shop, pulses are kept separate from soaps).

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3. Key Properties of Materials for Sorting

A. Appearance (दikhna / रूप-रंग)

• Materials look different from each other. Some look shiny, while others look dull.
• Lustre (चमक): Materials that have a shiny appearance are said to have lustre. These are usually metals (e.g., iron, copper, gold, aluminum).
• Dull Materials: Materials that lose their shine and look dull (e.g., wood, paper, cardboard).

B. Hardness (कठोरता)

• Hard Materials: Materials that are difficult to compress or scratch (e.g., iron, stone, glass).
• Soft Materials: Materials that can be easily compressed or scratched (e.g., sponge, cotton, foam).

C. Solubility in Water (जल में घुलनशीलता)

• Soluble Substances: Substances that completely disappear or dissolve in water (e.g., salt, sugar, vinegar).
• Insoluble Substances: Substances that do not dissolve in water and do not disappear even after stirring (e.g., sand, chalk powder, sawdust, oil).
• Note: Some liquids also mix with water (miscible like vinegar), while others form a separate layer (immiscible like mustard oil).

D. Transparency (पारदर्शिता)

• Transparent (पारदर्शी): Materials through which objects can be seen clearly (e.g., glass, clean water, air, some plastics).
• Opaque (अपारदर्शी): Materials through which we cannot see at all (e.g., wood, cardboard, metals).
• Translucent (पारभासी): Materials through which objects can be seen, but not clearly (e.g., oiled paper, frosted glass, butter paper).

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4. Important Summary Table

Property	Description	Examples
Lustrous	Having a shiny surface	Gold, Silver, Copper
Non-Lustrous	Dull appearance	Wood, Charcoal, Paper
Hard	Difficult to scratch/compress	Iron, Diamond, Brick
Soft	Easy to scratch/compress	Cotton, Sponge, Wool
Soluble	Dissolves in water	Sugar, Salt
Insoluble	Does not dissolve in water	Sand, Chalk, Oil
Transparent	Light passes through clearly	Glass, Air
Opaque	Light does not pass through	Wood, Metals
Translucent	Light passes partially	Oiled paper

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5. Important Keywords (महत्वपूर्ण शब्द)

• Classification (वर्गीकरण): Sorting into groups.
• Property (गुण): A characteristic feature of a material.
• Lustre (चमक): Shine of a material.
• Soluble (विलेय / घुलनशील): Able to dissolve.
• Insoluble (अविलेय / अघुलनशील): Unable to dissolve.
• Transparent (पारदर्शी): See-through.
• Opaque (अपारदर्शी): Not see-through.
• Translucent (पारभासी): Partially see-through.