试题与答案

请用学过的化学知识解释下列生产、生活实际中的一些现象或做法. (1)冬天建筑施工

题型:问答题

题目:

请用学过的化学知识解释下列生产、生活实际中的一些现象或做法.

(1)冬天建筑施工时往砂浆内掺入氯化钙以防冻.______.

(2)洗洁精易去除餐具上的油污.______.

(3)扑灭森林大火时设置隔离带.______.

(4)切过咸菜的铁质菜刀更容易生锈.______.

答案:

(1)冬天建筑施工时往砂浆内掺入氯化钙,会使混合物的凝固点降低,不易结冰,所以起到防冻作用;

(2)油污虽然不溶于水,但可以利用洗洁精的乳化作用把油污分割成很小的油滴而除去;

(3)灭火方法有:隔绝空气、降低温度到可燃物着火点以下、隔离可燃物,扑灭森林大火时设置隔离带即隔离了可燃物;

(4)铁生锈的条件是水分和空气,在食盐存在的环境中会加速生锈.

故答案为:(1)降低凝固点;(2)属于乳化作用;(3)隔离可燃物;(4)食盐的水溶液能促进生锈.

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题型:阅读理解

I felt excited, curious and nervous at the same time. I was excited because I would be skipping(跳级)two grades. I was curious because I didn't know how high school students were taught. However, I was most nervous at the idea that I would be doing high school homework.

I had just walked into the class when the bell rang. This wasn't a good start. But the kid in front of me looked very friendly. Luckily, since it was the first day of school, my teacher talked for about half of the period and  we just had the rest of the period to start the class. I didn't know what he was saying at first, but when I saw the problems on the paper, I knew what to do.

The next day, the kid said hi and I said hi back. We got into a conversation. It seemed that whenever I was talking to my friend, everyone stopped staring at (盯着看)me. Then the class started. It was easy. But I was still uncomfortable because I couldn't look around without meeting others’eyes, so I just kept my eyes on the whiteboard and on my textbook.

However, my friend didn't show up the next day, and the eighth graders just kept on staring at me. I didn't know why.

The next day everything changed. My friend was back to school. I was praised for my homework. Everyone stared at me less. Some started to be a little friendlier towards me. I felt at home at last here. My teachers also seemed pretty nice.

小题1:If the author didn't skip, he should study in _________ .

A.the fourth grade

B.the sixth grade

C.the seventh grade

D.the eighth grade小题2:What may make the author curious?

A.What his old friends are doing.

B.How high school students study.

C.How he will do his high school homework.

D.What the eighth graders' homework is.小题3:Why did the author always keep his eyes on the whiteboard and the textbook?

A.To pay attention to his teachers.

B.To attract his teachers' attention.

C.To follow his teachers' teaching.

D.To avoid meeting others' eyes.小题4:According to the passage, we know that the author ___________ .

A.got along well with his new class very soon

B.felt sorry about having skipped two grades

C.had one friend in his class all the time

D.got used to others' stares in the classroom

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题型:推断题

A~H都是初中化学中常见的物质,已知B为黑色固体,D为红色固体单质,F为红色固体,它们的转化关系如图所示。请回答:

(1)物质B的化学式为_________;

(2)反应①的化学方程式为_________________;写一个能实现反应④的化学方程式_________________;

(3)某兴趣小组利用反应③在实验室制取物质G。根据所得的物质G的质量,可求得参加反应的物质E的质量,但实际消耗的物质E的质量远远超过计算值,其原因可能是(从实验过程分析,任意答两点)_______________、_____________________。

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