Changes Around Us: Physical and Chemical
CBSE · Class 7 · Science
Quick revision notes for Changes Around Us: Physical and Chemical — CBSE Class 7 Science. Key concepts, formulas, and definitions for last-minute revision.
Key Topics to Revise
Types of Changes
- Changes can be observed through our five senses - sight, smell, touch, hearing, and taste
- All changes involve alteration in size, shape, smell, or other properties of substances
- Changes are classified into two main types: Physical Changes and Chemical Changes
Physical Changes - Detailed Study
- Examples: Folding paper, inflating balloon, crushing chalk, melting ice, boiling water
- The original substance remains the same, only appearance changes
- State changes (melting, freezing, evaporation, condensation) are physical changes
Chemical Changes - Detailed Study
- New substances are formed with different properties
- Examples: Rusting of iron, burning of magnesium, curdling of milk, cooking food
- Usually irreversible changes
Combustion - Special Type of Chemical Change
- Chemical reaction where substance reacts with oxygen producing heat and/or light
- Three requirements for combustion: Fuel (combustible substance), Oxygen, Heat (ignition temperature)
- Examples of combustible substances: wood, paper, cotton, kerosene, wax
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Sources & Official References
- NCERT Official — ncert.nic.in
- CBSE Academic — cbseacademic.nic.in
- CBSE Official — cbse.gov.in
- National Education Policy 2020 — education.gov.in
Content is aligned to the official syllabus. Refer to the board website for the latest curriculum.
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The World of Metals and Non-metals
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Adolescence: A Stage of Growth and Change
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