问题 多选题

如图是某同学设计的验证氧气约占空气总体积

1
5
的实验装置图.下列操作过程对实验结果的影响说法正确的是(  )

A.弹簧夹没夹紧会导致实验结果偏大

B.燃烧匙内盛放过量的红磷会导致实验结果偏大

C.没等装置冷却就打开弹簧夹会导致实验结果偏大

D.点燃红磷伸入瓶中时,没有立即塞紧瓶塞会导致实验结果偏大

答案

A、弹簧夹没夹紧,在红磷燃烧中,由于放热,导致装置的空气体积膨胀而逸出,最后进入装置内补充的水会更多,而使结果偏大.故此项正确.

B、燃烧匙内盛放过量的红磷不会影响实验结果,不能导致实验结果偏大,故此说法错误.

C、没等装置冷却就打开弹簧夹会使进入集气瓶中的水少,导致实验结果偏小,故此项错误.

D、点燃红磷伸入瓶中时,没有立即塞紧瓶塞会使集气瓶内空气逸出,导致实验结果偏大,此项正确.

故选AD

阅读理解

阅读理解

     My teenage son Karl became withdrawn after his father died. As a single parent, I tried to do my best

to talk to him. But the more I tried, the more he pulled away. When his report card arrived during his junior

year, it said that he had been absent 95 times from classes and had six falling grades for the year . At this

ate he would never graduate, I sent him to the school adviser, and I even begged him. Nothing worked.

     One night I felt so powerless that I got down on my knees and pleaded for help. "Please God, I can't

do anything more for my son. I'm at the end of my rope. I'm giving the whole thing up to you."

     I was at work when I got a phone call. A man introduced himself as the headmaster. "I want to talk to

you about Karl's absences." Before he could say another word, I choked up and all my disappointment

and sadness over Karl came pouring out into the ears of this stranger. "I love my son but I just don't know

what to do. I've tried everything to get Karl to go back to school and nothing has worked. It's out of my

hands."For a moment there was silence on the other end of the line. The headmaster seriously said, "Thank

you for your time", and hung up.

     Karl's next report card showed a marked improvement in his grades. Finally, he even made the

honor roll .In his fourth year, I attended a parent-teacher meeting with Karl. I noticed that his teachers

were astonished at the way he had turned himself around. On our way home, he said, "Mum, remember

that call from the headmaster last year?" I nodded. "That was me. I thought I'd play a joke but when I

heard what you said, it really hit me how much I was hurting you.  That's when I knew I had to make you

proud.

1. By saying "Karl became withdrawn", the author means that the boy changed entirely and _____.

A. preferred to stay alone at home

B. lost interest in his studies

C. refused to talk to others

D. began to dislike his mother

2. There was silence on the other end of the line because _____.

A. the speaker was too moved to say anything to the mother

B. the speaker waited for the mother to finish speaking

C. the speaker didn't want the mother to recognize his voice

D. the speaker was unable to interrupt the mother

3. The sentence "…he even made the honor roll" means that "_____".

A. he was even on the list to be praised at the parent-teacher meeting

B. he was even on the list of students who made progress in grades

C. he was even on the list of students who had turned themselves around

D. he was even on the list of the best students at school

4. What is the main idea of this passage?

A. Children in single-parent families often have mental problems.

B. Mother's love plays an important role in teenagers' life.

C. Being understood by parents is very important to teenagers.

D. School education doesn't work without full support from parents.

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