问题 实验题

刘佳同学设计了如下一组实验。取四朵用石蕊试液染成的紫色的干燥纸花,分别按下图进行实验。

回答下列问题:

(1)观察到纸花的颜色是: I. 纸花变红;II. _____________;III. 纸花不变色;IV. _____________。

(2)刘佳同学进行的I、II两项实验,说明了什么? _________________________________

(3)刘佳同学进行四组对比实验的目的是什么?(用文字叙述) ____________________________

(4)写出实验IV中发生反应的化学方程式: ________________________________

答案

(1)纸花不变色;纸花变红。

(2)稀盐酸能使紫色石蕊变红,水不使紫色石蕊变色。

(3)证明水和二氧化碳不使紫色石蕊变色,酸能使紫色石蕊变红。

(4)

单项选择题

We once had a poster competition in our fifth grade art class.

"You could win prizes," our teacher told us as she wrote the poster information on the blackboard. She passed out sheets of construction paper while continuing. "The first prize is ten dollars. You just have to make sure that the words on the blackboard appear somewhere on your poster. "

We studied the board critically. Some of us looked with one eye and held up certain colors against the blackboard rocking the sheets to the right or left while we conjured up our designs. Others twisted their hair around their fingers or chewed their erasers while deep in thought. We had plans for that ten-dollar grand prize, each and every one of us. I’m going to spend mine on candies one hopeful would announce while another practiced looking serious wise and rich.

Everyone in the class made a poster. Some of us used parts of those fancy paper napkins, while others used nothing but colored construction paper. Some of us used big designs and some of us preferred to gather our art tidily down in one comer of our poster and let the space draw the viewer’s attention to it. Some of us would wander past the good students’ desks and then return to our own projects with a growing sense of hopelessness. It was yet another grown up trick of the sort they seemed especially fond of making all of us believe we had a fair chance and then always—always—rewarding the same old winners.

I believe I drew a sailboat, but I can’t say that with any certainty. I made it. I admired it. I determined it to be the very best of all of the posters I had seen and then I turned it in.

Minutes passed.

No one came along to give me the grand prize and then someone distracted me and I probably never would have thought about that poster again.

I was still sitting at my desk thinking, what poster When the teacher gave me an envelope with a ten-dollar bill in it and everyone in the class applauded for me.

What was the teacher’s requirement for the poster()

A.It must appear in time.

B.It must be done in class.

C.It must be done on a construction sheet.

D.It must include the words on the blackboard.

单项选择题