1. Which of the following is a chemical change?   Rusting of iron   Boiling of water   Freezing of water   Dissolving of salt in water   Hint Half-n-half Clue   2. Solubility of a substance in a solvent usually increases with an increase in temperature.   False   True   3. Fill in the missing word Acid + _______ = Salt + Water   Base   Non Metal   Metal   Oxygen   Half-n-half Clue   4. Lemon juice is   Basic   Metallic   Neutral   Acidic   Half-n-half Clue   5. Acids change a litmus paper from   Blue to Red   Green to White   Red to Purple   Red to Blue   Half-n-half Clue   6. Catalysts often speed up certain chemical reactions.   False   True   7. The two allotropes of phosphorus are   Crystalline Phosphorus, Amorphous Phosphorus   Red Phosphorus, Yellow Phosphorus   Alpha Phosphorus, Beta Phosphorus   Rhombic Phosphorus, Monoclinic Phosphorus   Half-n-half Clue