1. The lead of a pencil mainly contains _______.   plastics   graphite   carbon black   lead   Hint Half-n-half Clue   2. A pH below 7 indicates _______.   presence of ions   purity of the sample   alkalinity   acidity   Half-n-half Clue   3. Which of the following is not a physical change?   Decantation   Precipitation   Oxidation   Distillation   Half-n-half Clue   4. Which of the following is not an allotrope of carbon?   Graphite   Silk   Diamond   Charcoal   Half-n-half Clue   5. Which of the following is not an acid?   H2SO4   HCl   NaOH   HNO3   Half-n-half Clue   6. Solubility of a substance in a solvent usually increases with an increase in temperature.   True   False   7. What is the combination of any substance with oxygen known as?   Oxidation   Reduction   Combustion   Hydrogenation   Half-n-half Clue