问题 选择题

在下 * * 种物质沸点的排列顺序中,正确的是(  )。

①正丁烷 ②2­甲基丙烷(CH3CH(CH3)CH3) ③戊烷 ④2­甲基丁烷 ⑤2,2­二甲基丙烷(C(CH3)4)

A.①>②>③>④>⑤

B.⑤>④>③>②>①

C.③>④>⑤>①>②

D.②>①>⑤>④>③

答案

答案:C

根据烃类的熔沸点大小判断规律:在有机物同系物中,随着碳原子数的增加,相对分子质量的增大,分子间作用力增大,熔沸点逐渐升高;分子式相同的烃,支链越多,熔沸点越低。分析各选项,①②均只有4个C原子,③④⑤均只有5个碳原子,故①②的沸点小于③④⑤的沸点;②有1个支链,而①无,故①>②;③无支链,④只有1个支链,⑤有2个支链,故③>④>⑤;综上所述:③>④>⑤>①>②。

单项选择题
阅读理解

阅读理解。

     A new research shows that in Britain more and more people are returning to the old tradition that the whole

family have a meal at table. Worrying about the obesity and breakdown of a family, people change their eating

habits so greatly, according to analysis. They find the number of the family having a meal together increases by

5% from 2002 to 2004, and most people who have meals with their family come from the rich social class.

     The new discovery makes doctors and the people struggling against obesity extremely excited. Giving up the

tradition that the whole family have a meal together is exactly one of the reasons for a series of problems

including children's overweight. If a child has a meal in front of the television or the computer alone, he will

often eat some fast food.

     Jason Collins is one of the persons returning to the old tradition. Collins is a manager of a bake (烘面包)

house. He finds after he gets used to having a meal at home with his child, the child becomes much more

obedient (听话的). Dr. Jin is a child psychologist, and she expresses welcome to this result of the study. She

says it can make parents have a very good chance to chat with the child when the whole family have a meal

together.

1. What makes people change their eating habit back to the old tradition in Britain? [ ]

A. Worrying about their children.

B. Worrying about some social problems.

C. Worrying about the living expense.

D. Worrying about health and family problems.

2. We can infer from the passage that _____. [ ]

A. people's eating habit has much effect on their family

B. most rich people have meals with their family

C. most children have the problem of overweight

D. most children don't like having dinner with the parents

3. How do the people who hope to lose weight feel about the new discovery?[ ]

A. They feel glad.

B. They feel surprised.

C. They feel sorry.

D. They feel disappointed.

4. Which of the following statements is TRUE according to the passage? [ ]

A. The child having dinner with his parents doesn't like watching TV.

B. Children become overweight all because of having dinner alone.

C. The family having dinner together is more united and friendly.

D. The reason a child has dinner alone is that he likes fast food.