问题 填空题

用所学化学知识回答下列问题:

(1)家用燃气热水器不完全燃烧产生的有毒气体主要是______.

(2)乱扔烟头不慎引起纸堆发生火灾,则烟头在引发火灾中的作用是______.

(3)形成酸雨的原因是空气受二氧化硫和氮氧化物的污染.酸雨给人类和环境带来的一种危害是______.防止酸雨形成的一种措施是______.

(4)扑灭森林火灾的有效方法之一是将大火蔓延线路前的一小片树木砍掉,其灭火原理是______.

答案

(1)家用燃气热水器不完全燃烧产生的主要有毒气体是一氧化碳;

(2)燃烧的条件是有可燃物、温度达到可燃物的着火点、与氧气接触,烟头引起火灾中烟头的作用是使温度达到可燃物的着火点;

(3)酸雨给人类和环境带来的危害有:影响人和动物的身体健康,腐蚀建筑物、金属材料,破坏土壤、植被等;减少化石燃料的燃烧可有效的防止酸雨形成;

(4)将大火蔓延线路前的一片树木砍掉使燃烧因缺少可燃物而停止;

故答案为:(1)一氧化碳;

(2)使温度达到可燃物的着火点;

(3)腐蚀建筑物;减少化石燃料的燃烧;

(4)隔离可燃物.

阅读理解

阅读理解。

    Young people can have problems with their minds. Some student becomes worried because they have to

study very hard. Others have trouble getting on well with people like their parents and classmates.

     Liu Wei, a junior 2 student from Hefei, could not understand his teacher and was doing badly in his lessons.

He became so worried about it that he started to cut his finger with a knife.

     Another student, 14-year-old Yang Fang from Guangzhou, was afraid of exams. She got very worried in

one, and when she looked at the exam paper, she couldn't think of anything to write.

     A recent report from Jiefang Daily says about 18% of Shanghai teenagers have mental problems. Their

troubles include being worried and very unhappy, and having problems in learning and getting on with people.

Many students who gave problems won't go for advice or help. Some think they will look stupid if they go to

see a doctor. Others don't want to talk about their secrets.

     Liang Yuezhu, an expert on teenagers from Beijing Anding Hospital has the following advice for teenagers:

    Talk to your parents or teachers often. 

    Take part in group activities and play sports. 

    Go to see a doctor if you feel unhappy or unwell.

1. The students who often become worried or have trouble getting on with others may have _____. [ ]

A. mental problems

B. a headache

C. knife with them

D. no parents

2. Liu Wei cut his finger with a knife because _____. [ ]

A. he was afraid of his teacher

B. he wanted to frighten his parents

C. he was so worried about his studies

D. his finger was badly hurt

3. Yang Fang's problem happened when _____. [ ]

A. she studied very hard

B. she had exams

C. she talked with her parents

D. she thought of something

4. Students who have problems won't ask others for help because _____. [ ]

A. they won't let others think they are stupid

B. they don't think doctors can help them

C. they think the problems are not serious

D. they have no secrets about others

5. Liang Yuezhu's advice tell us that _____. [ ]

A. it's unnecessary for them to be with others

B. only group activities and sports can help them

C. teachers and parents can't do anything about mental problems

D. it's better for the students who have mental problems to join others.

选择题