1. Which of the following is not a physical change?   Oxidation   Decantation   Precipitation   Distillation   Hint Half-n-half Clue   2. The lead of a pencil mainly contains _______.   plastics   carbon black   lead   graphite   Half-n-half Clue   3. Acids turn blue litmus paper _______.   red   pink   yellow   colorless   Half-n-half Clue   4. What is the combination of any substance with oxygen known as?   Hydrogenation   Combustion   Oxidation   Reduction   Half-n-half Clue   5. Which of the following is not an acid?   HCl   HNO3   H2SO4   NaOH   Half-n-half Clue   6. Which of the following gases is green in color?   Krypton   Neon   Chlorine   Hydrogen   Half-n-half Clue   7. A pH below 7 indicates _______.   alkalinity   purity of the sample   presence of ions   acidity   Half-n-half Clue