问题 计算题

塑料袋的广泛使用,给我们的日常生活中带来了便利。常用的塑料袋有两种,一种是用聚乙烯[(C2H4)n]制成的,另一种是用聚氯乙烯[(C2H3Cl)n]制成的。某化学兴趣小组的同学收集了一种日常生活中常用的塑料袋,对其组成进行了如下探究:

(1)Ⅰ鉴别和分析

①取样,用坩埚钳夹持在酒精灯上燃烧,火焰呈黄色,且无刺鼻气味;由此可以初步确定该塑料袋是可能是由              制成的(填“聚乙烯”或“聚氯乙烯”)。

②由于空气中氧气的体积分数为21%,因此用燃烧法确定塑料袋组成时,由于可能会生成既会产生污染,又会增加实验难度和实验误差的有毒气体                 ,故必须使用纯氧。

Ⅱ 设计与实验 同学们设计了如下图所示的装置,按下述步骤进行实验:

 ①连接好装置,检查气密性;②称取7.0g塑料样品,放入装置C中。称量D、E的质量; ③通入氧气一段时间后,加热塑料样品,使其燃烧;④塑料样品燃烧结束后,停止加热; ⑤继续通氧气至玻璃管冷却后,停止通氧气;⑥再次称量D、E的质量。

(2)思考与结论

①仪器F的作用是                           ;

②实验前将所用的塑料样品剪成碎屑的目的是                           

③将上述实验操作中的④、⑤颠倒可能导致的不良后果是                            ;

④若装置中没有连接仪器B,将使该塑料试样中氢元素的质量测算结果                           (填“偏小”、“偏大”、“无影响”中之一)

⑤实验后发现D、E装置分别增重9.0g、22.0g,则该塑料中碳、氢元素质量比为                          

⑥塑料由于难以降解,造成白色污染。请说出生活中减少白色污染的一点措施:                          

答案

(1) ①聚乙烯;②一氧化碳(或CO)

(2)

①防止空气中的二氧化碳被E中的烧碱溶液吸收而影响碳元素含量的测定结果(或防止空气中的CO2进入E装置);

②增大塑料样品和氧气之间的接触面积,使反应充分;

③液体会倒吸到玻璃管(烧管或平行管)中,导致其破裂(或D中液体倒流入C);

④偏大;

⑤6∶1;

⑥用布袋购物(其他合理答案均给分)。

阅读理解

阅读理解。

     I am a five-year-old elephant. When I was a baby, I lived in the wild with my parents. But some

hunters killed my mother, and they caught me. They sold me to this circus(马戏团) and a train carried

me here.

     I was born in a large family. My mother was the head of the family. As you might know, when a

female is born into the family, she never leaves.

Closely and happily, we travelled together, ate together, played together, and slept together. When I was

in the family, my mother and my sisters looked after me carefully. I played happily with all the other

elephants. Now, I miss them.

     You enjoy watching my wonderful tricks. To make you laugh, I have to perform(表演) eight hours a

day. But you may ask yourself, "How did they make that elephant stand on his head?" I never stood on

his head in the wild. I don't enjoy any of the tricks. I perform tricks because they make me do this or that. And still I hear you want to see me because you love me, you say. But you are thinking about yourself

what you want, what you like. Please think about me. If you love me, give me what I need. I need to be

free, and to be with my family. And you can watch me on videos, DVDs and Web pages.

1.Where was the elephant born?

A. In a zoo

B. In a circus

C. In the wild

D. In somebody's family

2. How is the elephant's mother?

A. She is in the circus now.  

B. She is still in the wild now.

C. She is the head of her family now.  

D. She died years ago.

3. What does the underlined (有画线的) word "they" mean?

A. The elephant's family members.  

B. The children who watch the tricks.

C. The other animals in the circus.    

D. The people in the circus.

4. What does the elephant want?

A. The children's love

B. To live with his family in the wild

C. To perform tricks

D. To travel in a train

5. Which of the following is NOT true?

A. The elephant enjoys making children happy.

B. Children love to see elephants in zoos or circuses.

C. People don't think much about how the elephant feel.

D. It's good to watch elephants on videos, DVDs and Web pages.

多项选择题