问题 选择题

下列关于胶体的叙述不正确的是(  )

A.分散质颗粒直径都在1~100nm之间

B.光线透过胶体时可发生丁达尔效应

C.鸡蛋白胶体置于空气中很快就会凝聚

D.Al(OH)3胶体能达到净水目的是使水中悬浮物沉降

答案

A.胶体区别于其它分散系的本质特征是分散质的微粒直径大小,胶体分散系的微粒直径在1~100nm之间,故A正确;

B.光线透过胶体时,胶体中可发生丁达尔效应,是胶体特有的性质,故B正确;

C.鸡蛋白胶体置于空气中会被空气中氧气氧化变质但不会很快就会凝聚,胶体聚沉需加入电解质或带相反电荷的胶粒的胶体或加热等方法,故C错误;

D.Al(OH)3胶体具有较大的表面积,能够使水中悬浮的固体颗粒沉降,达到净水目的,故D正确;

故选C.

阅读理解

阅读短文,从每小题所给的A、B、C、D四个选项中选出最佳选项。

      Helen Beckman, an old woman of fifty, always thought herself right. Sometimes she made a mistake, but

she tried her best to deny (否认) it.

     One day, she was walking along the street when she met with another woman. She remembered it seemed

like one of her friends. So she looked at her very carefully.

     Then she said, "Sandy Smith, my old friend! Well, well, well I haven't seen you for ten years." 

     She looked at the woman up and down. But the woman was puzzled (迷惹不解的) and couldn't know what

to say. 

     "But you've changed, Sandy," she went on. "You used to be fat but now you're thin." She smiled at the

woman again. "But, oh, you have changed," she said. "I've never known anyone change so much. You used to

have thick hair but now it's very thin. You didn't use to wear glasses but now you're wearing really thick ones." 

     She smiled at the woman again. 

     "But you're still the same Sandy Smith I used to have coffee with every week. We had some good times,

didn't we, Sandy?" 

     "Excuse me, madam," the woman said, "but my name isn't Sandy Smith."

     Helen thought for a minute, and then she said, "So you've changed your name as well, haven't you?"

1. Helen Beckman never thought _______. [ ]

A. she was too old.

B. she was free at home.

C. she did something wrong.

D. she was bad to her friends.

2. _______, so she looked at her up and down. [ ]

A. Helen Beckman didn't know the woman

B. Helen Beckman was not sure if the woman was her friend

C. Helen Beckman hoped to talk with the woman

D. The woman forgot to say hello to Helen Beckman

3. The man was puzzled because _______. [ ]

A. she didn't know Helen Beckman all

B. she forgot Helen Beckman was her friend

C. Helen Beckman changed greatly

D. Helen Beckman talked too much

4. _______, so she remembered her well. [ ]

A. Sandy Smith often wrote to Helen Beckman

B. Sandy Smith often went to see Helen Beckman

C. Sandy Smith was one of Helen Beckman's neighbours

D. Sandy Smith often had coffee with Helen Beckman

5. Which of the following is true? [ ]

A. Sandy Smith changed her name.

B. Helen Beckman made a mistake again.

C. Sandy Smith was much fatter than before.

D. Sandy Smith forgot her old friend.

单项选择题