问题 问答题

下面是某课外活动小组在进行探究乙醇性质实验时遇到的问题,请你帮助解决.

(1)在做乙醇与钠反应的实验时,把一小块钠缓慢放入装有乙醇的试管内,与钠和水反应相比有所不同:钠没有熔化成小球;钠先沉在试管底;反应后逐渐浮起.小组同学进行讨论,前两点现象解释达成共识.请说出你的看法.

钠没有熔化成小球,因为______;钠先沉在试管底,因为______

第三点现象解释存在争议,活动小组的同学形成两种意见:a生成的氢气产生浮力所致;b生成的乙醇钠增大了溶液的密度所致.请你设计一个实验验证a和b说法的合理性.______

(2)在做乙醇的催化氧化实验中,某同学有个意外发现:在酒精灯外焰灼烧铜丝观察到铜丝表面变黑;当铜丝接近灯芯,变黑的铜丝又恢复原来的红色.请用化学方程式解释上述变化过程.______.

答案

(1)钠与乙醇的反应是一个放热反应,但反应不如与水反应剧烈,相同时间内放出的热量少,温度没有达到钠的熔点,所以钠没有融化成小球;

钠的密度大于乙醇的密度,所以把钠加入乙醇中,钠沉到试管底部;

向完成实验的试管中再加入一小块钠,观察钠是浮在液面还是沉下去,从而确定合理说法.

故答案为:钠与乙醇反应不如与水反应剧烈,放出热量少,温度没有达到钠的熔点;钠的密度比水小比乙醇大,因而沉到试管底;向完成实验的试管中再缓慢加入一小块钠,观察钠是浮在液面还是沉下去;

(2)在酒精灯外焰灼烧铜丝观察到铜丝表面变黑,铜和空气中的氧气在加热条件下反应生成黑色的氧化铜,所以铜丝变黑2Cu+O2

.
2CuO;乙醇有还原性,氧化铜有氧化性,氧化铜和乙醇在加热条件下发生氧化还原反应生成铜和乙醛、水CuO+CH3CH2OH
CH3CHO+H2O+Cu.

故答案为:2Cu+O2

.
2CuO; CuO+CH3CH2OH
CH3CHO+H2O+Cu.

阅读理解

It may be the happiest place on Earth, but the Magic Kingdom has become a little more restrictive(限制的) for the children hoping to enjoy Disney’s US parks on their own. Beginning on March 23 of this year, anyone under the age of 14 must go there with someone over 14. If a worker who works at the front gates sees a child who looks younger than 14 without a person who looks older than that, he will have a talk with the tourist. If he is sure the tourist is under 14, his parents will be contacted to pick them up.

Before this, Disney did not have any age restrictions(限制) for tourists. The new rule was set up after Disney conducted a survey of its tourists and contacted various child welfare association(福利机构). They both thought it was necessary to have the age requirement. The American Red Cross suggested that 14 is the minimum(最小的) age for babysitters(保姆).

News of the age restriction comes nearly a week. A child on vacation with his father and mother fell into a pool and died at Disneyland Pop Century Resort(度假村). Anthory Johnson was swimming in the hotel pool with a group of children including his little brother and a cousin at about 9:30 pm when the accident happened. Witnesses said the teen was playing in the water on Sunday evening without family members. A cousin found him under water around 9:10 pm and told others in the group who pulled him out of water. Orange Country Sheriff’s officials said after Anthony was taken to nearby hospital, he died several days later.

小题1:How does the worker know the child is under 14?

A.By contacting with his parents.

B.By seeing if the child comes on his own.

C.By seeing if the child comes with his parents.

D.By looking at the child’s appearance and talking with him.小题2:What ISN’T the reason for setting up the new rule?

A.14 is the minimum age for babysitters.

B.Children like to play in Disney’s US parks with their parents.

C.Tourists think it’s necessary to have the age requirement.

D.A child on vacation with his parents died in a pool at Disney’s Pop Century Resort.小题3:What’s the main idea of this passage?

A.The happiest place for children.

B.A new rule of age requirement about children who go to Disneyland.

C.A survey of age requirement about children who go to Disneyland.

D.A child who fell into a pool and died at Disneyland.

单项选择题