问题 问答题

已知有两瓶溶质和溶剂均相同的溶液,一浓一稀.如何判断谁是浓溶液,谁是稀溶液?某学校化学兴趣小组就此展开讨论.

甲生认为:可用溶液的颜色深浅判断;

乙生认为:溶液的密度大小判断;

丙生认为:溶液与其他物质发生化学反应的速率大小判断.

请你判断甲、乙、丙三位学生的观点是否正确,并举例说明理由.______.

答案

甲生的观点适合于有颜色的溶液,乙生的观点适用于密度越大,溶质的质量分数越大的溶液,丙生的观点适用于反应有明显现象的溶液,

所以本题答案为:

(1)甲生的方法仅仅适用于有色溶液;如硫酸铜溶液,深蓝色的是浓溶液,浅蓝色的是稀溶液.

(2)乙生的方法通常适用于密度越大,溶质的质量分数越大的溶液.如硫酸溶液.而酒精溶液和氨水则相反.

(3)丙生的方法通常适用于反应时有明显现象的溶液.如锌与盐酸反应,气泡产生快的,反应速率大,是浓溶液.

阅读理解

My school makes students take one religion (宗教) class every year. But religion is really hard, especially with Mr Frank Smith for a teacher.

Mr Smith is 55 years old, with grey hair and a moustache (胡子). He always wears a blue school T-shirt, shorts and tennis shoes with long white socks. My friends say he looks like a cat.

In his class, we did yoga (瑜珈) and meditation (冥想) (actually most of the children in my class lay on the ground sleeping), tasted some strange tea, had classes outside in the garden, and watched videos and movies about Tibetan Buddhism (藏传佛教), God, and so on.

It was fun sometimes. However, the course (课程) was quite hard when it came to tests. The girls often worked until one or two o'clock in the morning on nights before the tests, but they still got bad scores.

When our test scores were bad, he would give us some makeup assignments (补考作业). Once I got a B, which I thought was bad, so I asked Mr Smith for an assignment to bring up my grades.

As a matter of fact, his assignments were often worse than the tests. The tests were just a lot of multiple-choice, fill-in-the-blanks, or short essays (文章). But his assignments usually included a speech in class.

I was not afraid of public speaking, yet it took me three days to collect the information, two days to write the speech, one day to make a PowerPoint and several hours to prepare. I knew my presentation (课堂展示) was good, because I saw Mr Smith's big smile when he listened to me. He gave me an A at last.

After finishing the course, I may not remember how hard it was or the meaning of some vocabulary. But through Mr Smith, I learned a lesson that will be with me my whole life. That is: no matter what we do, we need to put our hearts into it, and then our work will pay off.

小题1:The religion class is hard because Mr Smith _______.

A.uses strange ways to teach in his class.

B.never gives good scores, however hard you try.

C.gives difficult tests and make-up assignments.

D.likes students to make good presentations.小题2: How could students get good scores in Mr. Smith’s class?

A.Work hard by studying late into the night.

B.Remember all of the vocabulary.

C.Pay attention and take notes in class.

D.Do well on the make-up assignment.小题3:From the course, the writer learned that ____.

A.people should always be given a second chance

B.people should always put their hearts into their work

C.it is good to do yoga and meditation

D.it is good to choose strict teacher

单项选择题