Key facts

  • The 2026 CET Senior Secondary everyday science block is specific: chemistry, light, space and information technology, genetics, ecosystems, biotechnol...
  • Physical changes alter state, size or form, while chemical changes form new substances; oxidation, reduction and catalysts are common exam traps.
  • Metals, non-metals, salts, carbon compounds, hydrocarbons, CNG, polymers, soaps, detergents and Freons should be linked with daily uses and environmen...
  • Light questions focus on reflection laws, dispersion, lens types, and correction of myopia and hypermetropia.
  • Space and information technology includes India’s space programme, satellites, launch vehicles, remote sensing, communication and navigation uses.

Key Points at a Glance

  1. 1

    The 2026 CET Senior Secondary everyday science block is specific: chemistry, light, space and information technology, genetics, ecosystems, biotechnology, useful plants and animals, and human health must be revised together.

  2. 2

    Physical changes alter state, size or form, while chemical changes form new substances; oxidation, reduction and catalysts are common exam traps.

  3. 3

    Metals, non-metals, salts, carbon compounds, hydrocarbons, CNG, polymers, soaps, detergents and Freons should be linked with daily uses and environmental impact.

  4. 4

    Light questions focus on reflection laws, dispersion, lens types, and correction of myopia and hypermetropia.

  5. 5

    Space and information technology includes India’s space programme, satellites, launch vehicles, remote sensing, communication and navigation uses.

  6. 6

    Genetics requires terms such as gene, allele, chromosome, DNA, RNA, Mendel’s laws, central dogma and human sex determination.

  7. 7

    Ecology questions test ecosystem structure, biotic and abiotic factors, food chains, energy flow and biogeochemical cycles.

  8. 8

    Biotechnology, bio-patents, new plant varieties and transgenic organisms must be understood through agriculture, health, ethics and regulation.

  9. 9

    Economic importance of plants and animals connects food, fibre, medicine, pollination, livestock, fisheries, lac, honey and local livelihoods.

  10. 10

    Blood groups, Rh factor, transfusion safety, pathogens, human diseases and malnutrition need cause-prevention-cure style revision.

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Physical And Chemical Changes, Metals And Daily Compounds

A physical change alters appearance, size or state without making a new substance. Melting ice, dissolving sugar, cutting paper and evaporation are standard examples. A chemical change forms one or more new substances and is usually indicated by gas formation, colour change, heat or light, precipitate formation, or a hard-to-reverse change. Rusting of iron, burning of magnesium, curdling of milk and digestion are chemical changes. For CET, always ask: has the substance changed only in form, or has a new substance formed?

Oxidation and reduction are paired reactions. At school level, oxidation may be understood as gain of oxygen or loss of hydrogen, and reduction as loss of oxygen or gain of hydrogen. In the broader electron view, oxidation is loss of electrons and reduction is gain of electrons. Combustion, corrosion and rancidity are common oxidation examples. A catalyst changes the rate of a reaction without being consumed; enzymes in digestion are biological catalysts, and industrial catalysts make reactions faster or more economical.

Metals are generally lustrous, malleable, ductile and good conductors. Iron is used in construction but rusts in moist air; aluminium resists deeper corrosion because a thin oxide layer protects it; copper is used in wiring because it conducts electricity well. Non-metals such as sulphur, phosphorus and carbon usually do not show typical metallic properties, though graphite conducts electricity. Daily compounds matter more than rare formulas: common salt is sodium chloride, baking soda is sodium hydrogencarbonate, washing soda is sodium carbonate decahydrate and bleaching powder is used as a disinfecting and bleaching agent.

Takeaway: classify the change first, then connect the substance with its property, use and safety point.

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