问题 选择题

下列变化属于物理变化的是 (  )

A.钢铁生锈

B.海水晒盐

C.工业炼铁

D.木柴取暖

答案

A、钢铁生锈的过程中有新物质生成,属于化学变化,故A错误;

B、海水晒盐的过程中没有新物质生成,只是发生了水的蒸发,属于物理变化,故B正确;

C、工业炼铁过程中,碳发生了反应生成了新物质,属于化学变化,故C错误;

D、木柴取暖的过程中木柴燃烧释放了热,生成了二氧化碳等,有新物质生成,属于化学变化,故D错误;

故选B.

多项选择题 案例分析题
阅读理解

Facebook users may feel socially successful in the web world but they are more likely to perform poorly in exams. The majority of students who use Facebook every day are doing badly compared with those who don’t. About 83% of British 16 to 24-year-old people are using social networking site such as Facebook and MySpace, to keep in touch with friends and organize their social activities.

“Our study shows people who spend more time on Facebook spend less time studying,” said Aryn Karpinski, a researcher. “Every generation has its distractions(娱乐), but I think Facebook is a unique phenomenon.” Karpinski and a colleague questioned 219 US undergraduates and graduates about their study and general Internet use, as well as their specific use of Facebook. They found 65% of Facebook users accessed their account daily, checking it several times to see if they had received new messages. The amount of time spent on Facebook at each log-in(登录) varied from just a few minutes to more than an hour.

Some UK students have already realized the potential danger. Daisy Jones, 21, an undergraduate, realized the time she was spending on Facebook was threatening her grades, urging her to deactivate(使无效) her account, “I was in the library and tried to write a 2,000-word essay when I realized my Facebook habit had got out of hand,” she said. “I couldn’t resist going online, when thinking about it. Before you know it , a couple of minutes have turned into a couple of hours and you haven’t written a word.”

Jones is among the few to have realized the risks. 79% of the users, however, believed the time they spent on the site had no impact on their work. The CEO of Facebook said, “There is also academic research that shows the benefits of services like Facebook. It’s in the hands of students to decide how to spend their time.”

小题1:What can we know from Paragraph 1?

A.All the students who don’t use Facebook do well in exams.

B.Social networking sites have both advantages and disadvantages.

C.Facebook is the main site for British people to keep in touch.

D.Most of British students use social networking sites daily.小题2:Facebook users check their account frequently to ____________.

A.spend less time on study

B.make sure new messages aren’t missed

C.practise specific use of Facebook

D.accumulate amount of time spent on Facebook.小题3:Why did Daisy Jones deactivate her account?

A.She was warned about the risk of using Facebook.

B.Spending much time on Facebook affected her study

C.She wanted to write a long article in the library.

D.There was something wrong with her eyes.小题4:What’s the best title of the passage ?

A.Facebook fans do worse in exams

B.Social networking sites and their fans

C.Facebook helps organize social activities

D.How to use social networking sites correctly.