B. A new substance, hydrated iron oxide, is formed.
C. The color of iron changes.
D. It can be reversed by heating.
Answer: Option B
Solution (By JKExamLibrary)
Rusting is a chemical change because iron reacts with oxygen and moisture to form a completely new chemical substance, hydrated iron(III) oxide (Fe₂O₃·xH₂O), which has different chemical properties from iron and cannot be easily reversed by simple physical means like heating or cooling.
Explanation:
Phenolphthalein is colorless in acidic and neutral solutions, turning pink/magenta in basic solutions with pH > about 8.2-10. It is commonly used in acid-base titrations. Methyl orange is red in acidic and yellow in basic. Litmus is purple in neutral, red in acid, blue in base. Natural indicators like turmeric, beetroot also show color changes.
Explanation:
The head (–COO⁻) is ionic and attracted to water (hydrophilic). The long hydrocarbon tail is non-polar and hydrophobic, dissolving in grease. This amphiphilic nature allows cleaning.
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