📌 SECTION B · 6 × 2 = 12 MARKS (VSA)
Q21. A student performs an experiment (image). List two observations to justify that a chemical change has taken place.
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(i) Change in colour, (ii) Evolution of gas bubbles, (iii) Temperature change.
Q22. Draw labelled diagrams to show different stages of budding in Hydra.
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Budding in Hydra: bud appears, grows, develops tentacles, detaches. (Diagram description).
Q23 (a). Besides minimising loss of blood, why is it essential to plug any leak in a blood vessel? Name component of blood that helps.
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To prevent entry of pathogens. Platelets help in clotting by releasing thromboplastin.
Q24. Object at 60 cm from concave lens (f=30 cm). Find image position using lens formula.
🔍 VIEW ANSWER
1/f = 1/v – 1/u ⇒ -1/30 = 1/v + 1/60 ⇒ 1/v = -1/30 – 1/60 = -2/60 – 1/60 = -3/60 = -1/20 ⇒ v = -20 cm (virtual, same side).
Q25 (a). A wire of resistance R cut into three equal parts, joined in parallel. Find total resistance.
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Each part has R/3. Parallel: 1/Rp = 3/(R/3) = 9/R ⇒ Rp = R/9.
Q26. “Excessive use of chemicals and pesticides in agriculture adversely affect the environment.” Justify.
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Causes soil/water pollution, bioaccumulation, kills beneficial organisms.