问题 选择题

我们常用“往伤口上撒盐”来比喻某些人趁人之危的行为,其实从化学的角度说,“往伤口上撒盐”的做法并无不妥,甚至可以说并不是害人而是救人.那么,这种做法的化学原理是(  )

A.胶体的电泳

B.胶体的聚沉

C.血液中发生复分解反应

D.血液的氧化还原反应

答案

A、血液属于胶体,因为没有外接电源,所以不属于电泳,故A错误.

B、血液属于胶体,所以血液应具备胶体的性质,在遇到电解质溶液,加热,电性相反的电解质的时候都会聚沉.

在伤口上撒盐可以使伤口表面的血液凝结,从而阻止进一步出血,以及防治细菌感染,属于胶体的聚沉,故B正确.

C、血液和氯化钠不具备复分解反应的条件,所以不发生复分解反应,故C错误.

D、血液和氯化钠不发生氧化还原反应,故D错误发.

故选B.

完形填空

阅读下面的短文并回答问题,然后将答案写到答题卡相应的位置上(请注意问题后的词数要求)。

[1]I'm Jack.On July 14th,my family moved to Britain and excitement put me in a happy mood for weeks.

[2]After half a year self English training,I was sent into a local high schoo1.At the time I was extremely nervous.Students and teachers enthusiastically welcomed me and spoke to me very slowly,but I still hardly understood them.They liked me,because I was pretty outstanding in the math’s class.One day,a Russian guy challenged me and I put him on the ground by a bare hand.Since then,no one ever made a second challenge,and I got to know later that he was the strongest guy in the schoo1.I was actually quite proud as in China I never had chance to be seen like this.

[3]During the first two years of high school,I frankly didn’t achieve very much academically.The language put me down all the time.Needless to say,the British education system is very relaxing.I didn’t want to do as much work as before.It is terrific.

[4]Since the year 2000 I've taken great interest in designing and maintaining websites.With a large amount of effort and a small amount of time.I managed to construct a personal web.I gradually acquired the sense of professionalism and redesigned my sites again and again,and the first award or the official recognition was that my school put up my URL on their website as an example of the IT students’brilliance.

[5]I progressed.The flash version of the site won a few official website design awards.And I even started a business of web design.Nowadays,I devote much time in pursuit of Search Engine Marketing,which is vital to firms which heavily depend on internet sales.

小题1:Fill in the blank with one proper word.

When Jack moved to Britain,he was ______________________________________.

小题2:Which country might Jack come from?

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小题3:Which paragraph does the following sentence belong to?

Actually,I hadn't even attended an IT lesson.

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小题4:What did Jack succeed in establishing?(no more than 5 words)

________________________________________________________________________

小题5:What awards did Jack win?(no more than 5 words)

________________________________________________________________________

单项选择题