Which of the following processes involves a chemical change?
A. Magnetization of iron
B. Fermentation of sugar
C. Boiling of water
D. Melting of ice
Answer: Option B
Solution (By JKExamLibrary)
Fermentation of sugar (glucose) by yeast produces ethanol and carbon dioxide—new substances are formed, so it's a chemical change. Melting, boiling are physical state changes. Magnetization aligns domains but does not change chemical composition. Chemical changes involve breaking and forming of bonds. Indicators: gas evolution, color change, heat, precipitate.
Explanation:
Sodium lauryl sulfate (CH₃(CH₂)₁₁OSO₃Na) is a synthetic detergent with a sulfate group. Sodium stearate and potassium palmitate are soaps (carboxylate salts). Calcium oleate is soap scum.
Explanation:
NaOH is a strong base, fully dissociating into Na⁺ and OH⁻ ions. NH₄OH is a weak base. Ca(OH)₂ and Mg(OH)₂ are sparingly soluble but are considered strong bases in terms of dissociation of dissolved portion, but NaOH is the strongest among common ones.
Explanation:
Modern periodic law: The physical and chemical properties of elements are periodic functions of their atomic numbers. This was established by Moseley. Mendeleev's periodic law was based on atomic masses. Atomic number (Z) determines electronic configuration, which determines chemical behavior. Mass numbers vary with isotopes.
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