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问题 问答题 简答题

小结液体表面张力与分子结构间的关系，规律

答案

参考答案：

1，极性物质的r>非极性物质r，

2，结构相似的分子量增加，r增加，

3，含有环或者不饱和键的r>饱和碳氢氧化物，

4，一般有机物r，20-50mN/m，

5，r水是常见液体中最高的，r水为72mN/m，

6，熔盐及液体金属r最高，Hg：486.520℃，Fe：1880.1350℃，He：0.356K

选择题
计算：sin43°cos13°-sin13°cos43°的值等于（　　）
A．
3
B．
3
2
C．
2
2
D．
1
2
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填空题

动词填空。

1. If it             (rain) tomorrow, we _______ (not go) to the park.

2. The heavy rain prevented us _______ (play) football.

3. The teacher often tells us _______ (not make) any noise in class.

4. The doctor asked me ______ (take )the medicine three times a day.

5. When I met my friend on my way, I stopped             (talk) with him.

6. So much work usually makes him ______ (feel) very tired.

7. Sorry, we are late. We ______ (not catch) the bus.

8. There are not many cranes ______ (live) in the world.

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