1. The two allotropes of phosphorus are _______ and _______.   Red, Yellow   Rhombic, Monoclinic   Crystalline, Amorphous   Alpha, Beta   Hint Half-n-half Clue   2. A substance that absorbs moisture is called _______.   hydrophobic   hydrophilic   hygroscopic   amorphous   Half-n-half Clue   3. Catalysts speed up the rate of chemical reactions.   True   False   4. Heat is liberated in _______ reactions.   endothermic   substitution   exothermic   all chemical   Half-n-half Clue   5. Which of the following is not an allotrope of carbon?   Silk   Diamond   Graphite   Charcoal   Half-n-half Clue   6. What is the combination of any substance with oxygen known as?   Reduction   Combustion   Oxidation   Hydrogenation   Half-n-half Clue   7. The lead of a pencil mainly contains _______.   graphite   carbon black   lead   plastics   Half-n-half Clue