问题 问答题

某些食品的包装袋内一个装有白色颗粒状固体的小纸袋,上面写着“干燥剂,主要成分是生石灰”

(1)生石灰(CaO)可作干燥剂的理由是(用化学方程式表示)______.

(2)对它作了一系列探究,获得较多收益,其实验方案如下:

问题与猜想 实验步骤  实验现象 实验结论
 问题1:小纸袋中的物质能否继续作干燥剂?取足量小纸袋中固体放入烧杯中,加适量的水,触摸杯壁. _______________不能作干燥剂 
 问题2:猜想变质后的物质可能是______________________ ______________ _________________ 
(3)对它还有一个要再探究的新问题是:______.

答案

(1)生石灰与水极易反应生成氢氧化钙,故选CaO+H2O═Ca(OH)2

(2)对它的探究是分两个方面进行的:问题一是氧化钙不能做干燥剂,从表中的信息可以看出是利用氧化钙与水反应放出大量的热进行的.问题二:固体的成分检验主要依据下列知识:根据生石灰在空气中易吸收空气中的水变成氢氧化钙,氢氧化钙又易于空气中的二氧化碳反应生成碳酸钙的特点可知它可能为混合物为Ca(OH)2和CaCO3的混合物;再根据氢氧化钙的溶液呈碱性,能使酚酞试液变红,碳酸钙与盐酸反应生成是澄清石灰水变浑浊

故答案为:

问题与猜想 实验步骤 实验现象实验结论
问题1:小纸袋中的物质能否继续作干燥剂?取足量小纸袋中固体放入烧杯中,加适量的水,触摸杯壁. 杯壁温度无变化不能作干燥剂
问题2:猜想变质后的物质可能是氢氧化钙和碳酸钙的混合物取固体放入烧杯中加适量的水,溶解滴入酚酞试液,再滴加稀盐酸.酚酞变红,产生气泡,把气体通入澄清石灰水,溶液变混氢氧化钙和碳酸钙的混合物
(3)此题未开放题只要结合此题的物质问题合理即为正确.答案为:通过什么方法可重新让它做干燥剂

阅读理解

Look carefully at the back of a California state quarter. A man with a walking stick is pictured there. A bird called a California condor(大秃鹫)is flying overhead. Who is this man, and why is he so important that he is featured(处于显著地位)on the back of a coin?

The man on this quarter is John Muir. Even as a child, Muir loved watching nature. As a young man, he spent much of his life exploring the beauty of the wilderness. He walked more than a thousand miles across the country, through fields and woods. John Muir liked writing about the places he visited, describing their beauty.

Muir also wrote about problems. In order to create more farmland for sheep and cattle, many trees were being cut down. This made Muir unhappy and worried, because he knew that trees were important to forests and to the animals that lived in them.Muir believed that nature should be conserved(保护)instead of being changed by human beings. He wrote articles in magazines and newspapers to spread the word about conserving forests. Soon, others began to listen.

Muir wrote letters to important people, such as President Theodore Roosevelt. The president admired Muir’s love for nature. When Roosevelt came to visit Muir in California. Muir convinced(说服)the president to go camping with him for three nights under the trees so they could talk about conservation. Later, President Roosevelt set aside 148 million acres of land for national forests and established(建立)five national parks. National parks are large areas of land that are protected from development. This means that people cannot build homes or businesses there. One of these parks is Yosemite National Park, the area that is featured on the back of the California quarter.

Though it has been almost one hundred years since John Muir died, people continue his work today. His work as a conservationist helped us to see the beauty of our natural world. John Muir made us understand the importance of protecting our earth and our resources---then, now, and for the future.

小题1:Why did President Theodore Roosevelt visit John Muir?

A.Because Roosevelt loved watching nature.

B.Because Roosevelt received letters from John Muir.

C.Because Roosevelt admired John Muir’s love for nature.

D.Because Roosevelt was sad about the problems with farmland.小题2:Why is John Muir featured on the back of a California state quarter?

A.Because he walked over a thousand miles across the country.

B.Because he helped people understand the importance of protecting the natural world.

C.Because he wrote articles to spread the word about conserving forests.

D.Because he once wrote several letters to President Theodore Roosevelt.小题3:What is the writer’s purpose of writing this article?

A.To advise readers to become active conservationists.

B.To make us interested in the story about a great man.

C.To tell us something about an important person in history.

D.To give information about how to conserve the environment.

判断题