题干

同学们在学习金属与盐溶液的反应时,老师强调:“金属K、Ca、Na必须除外.”化学兴趣小组的同学们对此产生了兴趣,并在老师的指导下,进行如下探究:

【提出问题】将金属钠投入到硫酸铜溶液中,结果会怎样?

【查找资料】(1)少量钠通常保存在煤油中;(2)钠是银白色的软金属,可用小刀切割,熔点97.81℃,沸点882.9℃,密度为0.97g/cm3(3)钠是一种很活泼的金属,遇水发生剧烈反应,生成氢氧化钠和氢气.

【做出猜想】猜想Ⅰ:放出气体,生成蓝色沉淀,能置换出铜;

猜想Ⅱ:放出气体,生成蓝色沉淀,不能置换出铜.

【实验探究】

实验操作

实验现象

①取10ml一定溶质质量分数的硫酸铜溶液,倒入50ml的烧杯里

②取一块钠,用滤纸吸干表面煤油,再切取绿豆大小的一块,投入溶液中

钠浮在液面上,熔化成闪亮小球,钠球游动,发出“嘶嘶”的声响,析出蓝色沉淀

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    The world has many beautiful sounds. We can hear the songs of birds and the laugh of people. We can listen to the cool music and news reports. And it's all because of our ears! They bring us a world of sounds. But some people can't hear any sound at all. Some are born deaf. Others can hear well in their childhood, but too many loud sounds hurt their ears later on. Many people in China can't hear ordinary sounds clearly. A large number of them are children. Most of them are born with good hearing. But six children of every 1,000 have hearing problems when they are born. And if a child has hearing problems, he or she usually will also have some learning problems at school. A lot of things can cause hearing problems. For example, too much earwax is not good for our hearing. And noise louder than 85 decibels (分贝) can hurt our ears and make us lose our hearing for a short time or even for ever. Hearing is important for all of us. So we should do our best to give our ears special care. Don't forget to do the following:

● Try to stay away from places with too much noise. If you have to go, wear earplugs. A pair of good earplugs can cut the noise by 30 decibels. ● When swimming, remember to put earplugs into your ears to stop water from getting in.

● Never put anything sharp into your ears. If you think you have too much earwax, ask your mum or dad to help you clean it out. Keep these things in mind! Then you won't be saying “WHAT? WHAT?" when you are older.