下列物质的用途主要利用其化学性质的是（ ）
A．石墨棒作干电池电极
B．小苏打可做面粉发酵剂
C．干冰用于人工降雨
D．铜用于制造导线
答案：B
题目分析：石墨棒作干电池电极，是利用石墨的导电性；干冰用于人工降雨，因为干冰升华会吸热，使水蒸气凝结成小水珠；铜用于制造导线，利用铜的导电性；这些都是利用物质的物理性质；小苏打可做面粉发酵剂，因为小苏打能与发酵面团中产生的酸反应，产生二氧化碳气体，致使做出的面食喧软多孔，这利用了小苏打的化学性质。选B。
点评：本题难度不大，物理性质是指物质不需要发生化学变化就能表现出来的性质，如颜色、状态、气味、味道、熔点、沸点、硬度、密度、溶解性、导电性、挥发性、吸附性等；化学性质是物质在化学变化中表现出来的性质，如可燃性、氧化性、酸性、碱性等。
| 完形填空 。 Health is far more important than wealth (财富) and wisdom (智慧). Good health makes us enjoy our 1 and achieve what we hope for in our future life. But poor health makes us become 2 interested in everything around us. How to stay healthy is very important to everyone, 3 we have lots of good medicine. When we discuss this, we must pay attention to some rules in mind. Firstly, it is very important for us to 4 more fruit and vegetables because they provide vitamins, and they can keep us in good health. Secondly, we have to 5 a balanced diet and regular eating habits. Proper nutrition (营养) is important for good health. Don't eat food 6 lots of sugar and fat. Eat plenty of food high in protein(蛋白质). Thirdly, we'd better do morning exercises every day. Enough sports can make our bodies strong. 7 , we shouldn't have too much work pressure. Getting too tired all the time may make us become weak when we meet some sudden accidents, and it can also make us __8 get sick. Finally, we have to 9 those bad habits that make us unhealthy, such as drinking and smoking. In a word, if we pay attention to the things according to the rules 10 above, we'll lead a healthy life and become as fit as we wish. | ||||
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