问题 问答题

将ZnCO3、Cu2O和足量的木炭粉混合,加热到800℃左右,充分反应后得到一种外观似黄金的合金.为了确定该合金的成分,进行如下探究:

【提出猜想】该合金中一定含有铜、锌,可能含有木炭粉.

【设计实验】(1)证明该合金中铜、锌的存在,将有关内容填入下表中.

实验目的实验操作实验现象
①将合金加工成粉末取一小块合金进行研磨
②证明锌的存在
③证明铜的存在
(2)若该合金中混有木炭粉,如何将木炭粉除去以得到铜锌合金?简述实验操作.

答案

【设计实验】②设计实验,锌可以和盐酸反应生成气体,而铜不能,所以可以用稀盐酸来验证锌的存在,若产生气泡则证明存在锌,反之不存在;

③铜可以和氧气反应生成黑色的氧化铜,所以可以将合金样品进行灼烧后,如果变黑则说明存在着铜粉;

(2)根据碳的性质可以知道,碳可以和二氧化碳反应,所以可以在对混合物进行高温加热,然后向其中通入二氧化碳来除去碳粉.

故答案为:(1)

  实验目的    实验操作    实验现象
  ② 取少量合金样品加稀盐酸 有气泡冒出
取合金样品在空气中灼烧合金表面变黑
(2)取合金粉末于试管中通入CO2并高温加热.

阅读理解

LaMar Baylor, an American performer in the Broadway musical, spends most of his time in New York City.But since 2011, he has also spent weeks in Kigali, the capital of Rwanda.There, he teaches dance to boys who live on the street.His teaching is part of an effort by the Rebecca  Davis Dance Company.The project helps young people learn more about dance and learn how to  behave in a classroom environment.

Rebecca Davis and LaMar Baylor teach ballet to street children in Kigali, Rwanda.The  children have lost all of their families.Some have been in prison; others have sold their bodies for sex.Dance classes provide the children with structured learning and self-expression that they've never had before.

Rebecca Davis is the founder and director of the dance company.She got the idea for the project after visiting Rwanda in 2008.There she met a large number of street children who were dancing, and she thought that dance could be used to get them off the street and into a safe place.She believes that learning to dance is a step toward education.She says children can take classes in information and technology after they have learned to attend classes and follow directions.

Boys who have done best in the classes win scholarships and are sent to the Sunrise Boarding School.About 30 boys have won this kind of financial aid.

As for LaMar Baylor, he knows from his own experience how dance can lead to a better life.He is from Camden, New Jersey.Camden has sometimes been called America's poorest and most dangerous city.He now thanks dancing for saving his life.

The Rwanda program is the largest one set up by the Rebecca Davis Dance Company, and Ms.Davis has also set up dance programs in Bosnia-Herzegovina and Guinea.About 2,000 children in the three countries have taken part in the project since it was begun in 2010.

小题1:The dance project aims to____.

A.give the street children parental care

B.provide scholarship for the street children

C.help the street children receive some education

D.keep the street children in good health小题2:What do we learn about the street children from the passage?

A.All of them can be sent to the Sunrise Boarding School.

B.It may be hard for them to adapt to classroom rules at first.

C.They only take classes in dancing.

D.Many of them have been in prison.小题3:What LaMar Baylor and the street children in the project have in common is that _.

A.they all benefit from dancing

B.they borrowed money from the project

C.they learn to express themselves in dance class

D.they were homeless at one time小题4:We can infer from the last paragraph that          -.

A.the dance project was started in Guinea

B.the Rwanda program is the first program by Rebecca Davis

C.the Rwanda program has attracted about 2,000 children

D.the dance project gains popularity and grows quickly

判断题