Ch 5 introduces acids, bases, and salts. Students learn to test substances using indicators (litmus, turmeric), understand the neutralisation reaction, and see how it applies in daily life.
Acids taste sour (lemon juice, vinegar). Bases taste bitter and feel soapy (baking soda, soap). Indicators change colour to identify acids/bases: blue litmus turns red in acid; red litmus turns blue in base. Neutral substances (water) do not change litmus.
Acid + Base → Salt + Water. This is the neutralisation reaction. Examples: antacid (base) neutralises excess stomach acid. Farmers add lime (base) to acidic soil. Factory waste (acidic) is neutralised before release.
Download: https://ncert.nic.in/textbook/pdf/gesc105.pdf | Complete book: https://ncert.nic.in/textbook/pdf/gesc1ps.zip
Natural indicators are substances from plants that change colour in acids and bases. Litmus is from lichen. Turmeric turns red/brown in bases. China rose (hibiscus) turns dark pink/magenta in acids and green in bases.
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