问题 问答题

如图是空气中氧气含量的测定装置,回答下列问题:

(1)指出有关仪器的名称:A______,B______.

(2)盛放在仪器A中的物质是______,该物质燃烧时的现象是______,该反应可用文字表示为______.

(3)实验中,若仪器A中的物质质量太小,测得氧气的体积分数(填“偏大”或“偏小”或“不变”下空同)______,若钟罩的密封性不好,测得氧气的体积分数______.

答案

(1)测空气成分的该试验操作中所用的仪器A为燃烧匙、B为水槽;

(2)该试验操作中燃烧匙内盛放的药品是红磷;红磷燃烧时发生的现象是产生大量的白烟;红磷燃烧的文字表达式为:磷+氧气

点燃
五氧化二磷;

(3)在此实验中,若燃烧匙内放红磷量少,其燃烧时消耗不尽钟罩内空气中的氧气,钟罩内气压减小达不到试验预期目标,因而测得氧气的体积分数偏小;若钟罩的密封性不好,红磷燃烧消耗氧气,使钟罩内气压减小,外界空气就会进入钟罩内,这样进入里面的水达不到实验预期目标,因而测得氧气的体积分数偏小.

故答案为:(1)燃烧匙;水槽

          (2)红磷;产生大量白烟;  磷+氧气

点燃
五氧化二磷        

          (3)偏小;偏小

完形填空

I first had physics lessons when I was in Grade Eight some years ago. In class, I   1   that there wasn’t a Nobel (诺贝尔) Prize winner from China. That made me sad, and I decided to change (改变) it.   2   after that, I got up early in the morning. I turned on the light and took out a physics book. Then I started   3   quietly. I worked so hard because I had a great   4   — one day, I would be the first   5   person to win the Nobel Prize in physics. Later on, I found physics at school too easy for me. I wanted to learn   6  , so I made a reading plan and started to find answers to more difficult problems.

Now I am a top student in physics. I won the first prize in the national physics competition  last month. And I am happy to be closer to my dream after a few   7   hard work. Of course,   8   I have some problems. My classmates always   9   me when they are talking about fashion (时尚) or pop stars, because I know   10   about them. “Well, that doesn’t matter too much,” I tell myself. “They don’t know much about physics , but I won’t laugh at them.”

小题1:A. joined           B. heard                 C. studied

小题2:A. So              B. But                    C. And

小题3:A. writing         B. reading                C. thinking

小题4:A. dream          B. idea                 C. plan

小题5:A. Chinese        B. Canada                C. American

小题6:A. much           B. more                  C. most

小题7:A. weeks’         B. months’              C. years’

小题8:A. usually         B. always                C. sometimes

小题9:A. depend on      B. look at                C. laugh at

小题10:A. anything        B. nothing              C. everything

问答题 简答题