1. Acids turn blue litmus paper _______.   red   pink   yellow   colorless   Hint Half-n-half Clue   2. The lead of a pencil mainly contains _______.   carbon black   graphite   plastics   lead   Half-n-half Clue   3. Lemon juice is _______ in nature.   metallic   basic   acidic   neutral   Half-n-half Clue   4. Heat is liberated in _______ reactions.   substitution   endothermic   all chemical   exothermic   Half-n-half Clue   5. A substance that speeds up the rate of a chemical reaction without undergoing any change itself is known as a _______.   catalyst   cation   nucleus   counter ion   Half-n-half Clue   6. What gas is evolved when dilute sulfuric acid is added to zinc?   Hydrogen   Hydrogen Peroxide   Argon   Sulfur Dioxide   Half-n-half Clue   7. Which of the following is not a physical change?   Oxidation   Distillation   Decantation   Precipitation   Half-n-half Clue