Answer Chemistry
Answer Key Section A Chemical reaction: A process in which one or more substances undergo a chemical change to form new substances with different properties. Observable sign: Change in colour / evolution of gas / change in temperature / formation of precipitate (any one). Balanced chemical equation: An equation in which the number of atoms of each element is the same on both sides. Combination reaction: A reaction in which two or more substances combine to form a single product. Example: CaO + H₂O → Ca(OH)₂ Type of reaction: Decomposition reaction. Corrosion: The gradual destruction of metals due to reaction with environment. Example: Rusting of iron. Chemical formula of rust: Fe₂O₃·xH₂O (hydrated iron(III) oxide) Rancidity: Oxidation of fats and oils leading to unpleasant smell and taste. Section B (2 × 6 = 12 marks) Balanced equation: 3Fe + 4H₂O → Fe₃O₄ + 4H₂ Steps to balance a chemical equation: Write the skeletal equation Li...