1. Oxygen cannot be further subdivided into simpler substances by any physical or chemical means. Therefore, it is _______.   a mixture   a compound   an element   Hint Half-n-half Clue   2. Potassium sulfide solution is a _______ mixture.   homogeneous   heterogeneous   3. Which of the following is a mixture?   Potassium carbonate solution   Potassium carbonate   Potassium   Half-n-half Clue   4. Which of the following is a compound?   Sodium   Sodium sulfide solution   Sodium sulfide   Half-n-half Clue   5. A mixture of water and oil is _______ in nature.   heterogeneous   homogeneous   6. Which of the following is an element?   Calcium chloride solution   Calcium   Calcium chloride   Half-n-half Clue   7. Copper sulfate can be further subdivided into simpler substances by chemical means only. Therefore, it is _______.   a compound   an element   a mixture   Half-n-half Clue