1. What is the combination of any substance with oxygen known as?   Combustion   Oxidation   Hydrogenation   Reduction   Hint Half-n-half Clue   2. Which of the following is not a physical change?   Distillation   Decantation   Precipitation   Oxidation   Half-n-half Clue   3. Which of the following is a chemical change?   Boiling of water   Freezing of water   Dissolving of salt in water   Rusting of iron   Half-n-half Clue   4. Lemon juice is   Basic   Metallic   Acidic   Neutral   Half-n-half Clue   5. Heat is liberated in   All chemical reactions   Exothermic Reactions   Endothermic Reactions   Substitution Reactions   Half-n-half Clue   6. Which of the following gases is green in color?   Neon   Chlorine   Krypton   Hydrogen   Half-n-half Clue   7. Catalysts often speed up certain chemical reactions.   False   True