问题 问答题

某同学根据日常经验推测,可燃物燃烧可能与氧气和温度有关,设计并完成了下列实验进行验证:

小题1:白磷燃烧的化学方程式为

小题2:实验   和实验   证明了可燃物燃烧必须要接触氧气。

小题3:实验   和实验   证明了可燃物燃烧必须要达到一定温度。

小题4:瓦斯(主要成分为甲烷)爆炸是煤矿安全事故的一种。为了生产安全,要求井下通风状况良好。控制天然气浓度在1%以下;禁止拾烟草及点火工具下井。挖掘时了防止和减少摩擦火花的产生。上述措施可以防爆是甚为破坏了燃烧的某些条件,分别是

答案

小题1: 4P+   5O2 =  2P2O5

小题2:实验②和实验④

小题3:实验③和实验④ 

小题4:隔离了可燃物、降低温度到着火点以下

实验①将白磷放在冷水中白磷不能燃烧,白磷的着火点是40℃,白磷是一种易燃物

实验①温度没有达到白磷的着火、没有和氧气接触应此白磷不燃烧。实验②白磷放在热水中不能燃烧,白磷没有接触到氧气。实验③在冷水中的白磷通入氧气白磷任然没有燃烧,没有温度没有达到着火点,故白磷不能燃烧。实验④中的白磷燃烧了,是因为白磷与氧气接触、温度达到了白磷的着火点,故白磷能够燃烧。燃烧需要3个条件可燃物、温度要达到着火点、要与氧气接触

阅读理解

任务型阅读.。

     Everyone has got two personalities: one is shown to the world and the other is secret and real . You don’t show your secret personality when you are awake , but when you are asleep,  your sleeping position (睡姿) shows the real you . Different sleeping positions represent different personalities .

     If you go to sleep on your back , you are a very open person . You normally trust people and (2)you

are easily influenced by fashion or new ideas . You don’t like to disturb others , so you never express your real feelings . You are quite shy and you aren’t very confident .

     If you sleep on your stomach , you are a quiet person . You worry (1)_________ and you are always easily upset . You are very stubborn , but you never ask too much . You usually live for today not for

tomorrow . This means that you enjoy having a good time .

     If you sleep curled up (蜷卧) , you are probably a very nervous person . You are shy and you don’t

normally like meeting people . You like to be on your own . You are easily hurt .

1. 在(1)处横线上填上适当的词组,使上下文通顺:

_______________________________

1.将划线部分(2)译成汉语:

_______________________________

2.How many sleeping positions are mentioned in this passage ?

_______________________________

3.找出文中与下列句子意思相近的句子。You prefer to be alone .

_______________________________

4.找出文中最能表达该短文主旨的句子:

_______________________________

单项选择题