问题 选择题

物质的性质决定其用途。下列因果关系不成立的是

A.镁燃烧能发出耀眼的白光,所以可用于制作照明弹

B.因为磷燃烧能产生白烟,所以可用于制作烟幕弹

C.因为氮气化学性质不活泼,所以可用作保护气

D.因为氧气能支持燃烧,所以可用作燃料

答案

答案:D

A、制作照明弹必须很亮发出白光,镁燃烧发出的白光就可以,故A说法正确;

B、磷燃烧生成五氧化二磷是固体颗粒属于白烟,使空气的透明度降低可以做烟幕弹,故B说法正确;

C、保护气必须化学性质稳定,不易和其他物质反应,氮气化学性质就不活泼,所以可以做保护气,故C说法正确;

D、燃料必须本身能够燃烧,氧气只能支持燃烧,本身不能燃烧,不能作燃料,故D说法错误.

故选D.

写作题

下面是一位同学在学校论坛上发的帖子。假设你是Mary, 请根据他的这三个问题给出你的建议。开头已给出,字数:70词左右 。

Dear friend, 

What a terrible day today ! This morning I was late for school again and my teacher was very angry with me. Then I found I left my math book at home. Because I played computer games too late last night, I fell asleep in class this afternoon. I didn’t hear what the teacher said. I didn’t know how to do my homework. I really don’t know what to do. Could you please give me some advice?

Yours,

Looking for help

参考词汇:make mistakes, say sorry to... ;  get...ready ;   listen carefully in class;                     spend more time on...;help...with..

Dear looking for help ,

Here is some advice for you .

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Yours,                      

Mary 

填空题