1. The lead of a pencil mainly contains _______.   graphite   carbon black   lead   plastics   Hint Half-n-half Clue   2. What is the combination of any substance with oxygen known as?   Combustion   Hydrogenation   Reduction   Oxidation   Half-n-half Clue   3. Fill in the missing word: Acid + _______ = Salt + Water   Base   Oxygen   Metal   Non Metal   Half-n-half Clue   4. A pH below 7 indicates _______.   purity of the sample   presence of ions   alkalinity   acidity   Half-n-half Clue   5. Heat is liberated in _______ reactions.   substitution   exothermic   all chemical   endothermic   Half-n-half Clue   6. The 'fizz' in soft drinks is caused by _______.   helium   hydrogen   Carbon dioxide   nitrogen   Half-n-half Clue   7. Catalysts speed up the rate of chemical reactions.   True   False