题干

设计并完成以下探究实验.
【实验目的】a.探究燃烧的条件;b.测定空气中的氧气的含量.
【查阅资料】白磷的着火点是40℃,熔点44.1℃,红磷的着火点是240℃.
【实验步骤】
Ⅰ将足量白磷和红磷分别放在A,B两个大试管中;
Ⅱ在试管口分别套上白色、红色的瘪气球,并用细线固定住,然后将其同时浸在盛有80℃热水的烧杯中(如图所示).
Ⅲ取出A试管,待____ 后,将其倒立在冷水中,在水下取出气球,用毛玻璃片盖好,取出试管.
【实验现象】
1,步骤Ⅱ中,A试管中白磷燃烧,产生白烟.同时,白色气球____ ;
2,步骤Ⅱ中,B试管中的红磷无变化;
3,步骤Ⅱ中,热水中的白磷____ 但不燃烧;
4,步骤Ⅱ中,最终试管中的水约为试管体积的
1
5
.
【问题讨论】
(1)现象1中,白气球发生上述变化的原因是:____ ;
(2)现象1与3说明可燃物燃烧需要氧气;现象____ (填序号)说明燃烧需要使可燃物的温度达到着火点;
(3)如开始实验时气球未捏瘪,则最终A试管中水的体积中将____ (填“偏大”、“偏小”或“不变”).
上一题 下一题 0.0难度 选择题 更新时间:2019-02-23 05:37:24

答案(点此获取答案解析)

冷却,先变大后边小,融化,白磷燃烧放出大量的热,消耗氧气,1、2,偏小

同类题5

根据短文内容,从短文后的选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。

AfterSteve Jobs died, his friend Larry Ellison said something like this, “There willnever be another Steve Jobs.”____ Larry wrote this list of Steve's life lessonsto remind us all.

Love what you do.

SurelySteve became a billionaire when he brought Apple back. Apple was hiscalling—even after he got fired from the company. We all have bad jobs at onepoint in our lives. But the question is:amI in the right job? Have I found the right company? Life doesn't go on forever.____

Don't do it all by yourself.

Stevelearned a great leader can't do it all by himself. He needs people. They mustbe talented.____ They must be given the opportunity to succeedand fail. In short,youhave to learn to be a great leader if you want to see your great ideas and hardwork truly have an influence on the world.

____Appleis always the best at creating a new product that meets the exact needs ofusers. It's empathy (同情心)that helps Apple achieve this. Whenever the user has the first touch with a newApple product, he says“Wow, it's just what I need.” Remember: you're King inthe business world if you know exactly what consumers desire.

Don't mess around with your health.

____ That's the most important lesson from Steve'slife. It's great to learn from him now, but the fact is that he should still behere if he had treated his cancer properly. Instead, Steve chose a naturopathic(自然疗法的)solutionthat wasn't effective. When he finally decided to take his doctor's originaladvice ,itwas too late.

A.They must be inspired.

B.Be the best in your field.

C.Take your health seriously.

D.Get on your right path now.

E.Will this lead to a successful career?

F.Put yourself in the other person'sshoes.

G.What are the key things that we canlearn from him?