题干

请从A或B两组趣味实验中任选1个作答,若两题均作答,按A计分。

A

B

向一盛有少量干冰的玻璃容器中加入适量热水,立即产生浓厚的白雾,产生此现象的原因是____

另取一盛有适量澄清石灰水的玻璃容器,向其中加入少量干冰,观察到澄清石灰水变浑浊,发生反应的化学方程式为____。

点燃蜡烛后,电子秤示数逐渐减小。蜡烛减小的质量____(填“大于”“等于”或“小于”)燃烧后生成物的总质量。

用玻璃杯迅速扣住燃烧的蜡烛,并使杯口始终浸没在水中最终杯中液面____(填“高于”“等于”或“低于”)碗中液面。

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答案(点此获取答案解析)

干冰升华吸热,使周围的水蒸气冷凝成小水滴,CO2+Ca(OH)2=CaCO3↓+H2O,小于,高于

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    I have received many Christmas gifts over the years. The best gift I ever received was presented to me 1 a stranger. I never even knew his name and I only had contact with him 2 less than 60 seconds. His Christmas present to me changed 3 way I think about people and about Christmas.

    I hate Black Friday sales. It's often a gathering of people 4 are there for many different reasons. Some are looking for one item for their loved one, or perhaps themselves. Their purpose are completely have 5 to do with the festive time of year, and can merely be summed up with one word, "Cheap!"

    It was several years ago when my wife asked me 6 her at the local department store on Black Friday morning. They had advertised a child's bike 7 she wanted to purchase for our son. We stood with a very large crowd, waiting for the manager to blow the whistle(口哨). I told my wife 8 we got a bike, fine, but if we did not, I was OK with that too.

    As 9 bikes began to gradually(逐渐)decrease in size, I saw my "polite" opportunity to reach my hands around the corner of one of the boxes. I 10 it and suddenly felt some mild resistance(阻力). I looked up to see one of 11 gentlemen I had ever seen in my life. Frightening was not the word to describe his appearance. He was wearing lots of straps of metal spiked leather(带有铆钉的皮带) around 12 arms and even his neck and he had tattoos(纹身)too.

    I started to return the box 13 he gently pushed it back in my direction and back into my hands. He then directed it into my shopping car. He looked at me, smiled, and said, "Merry Christmas." All the way home I 14 that this moment was by far the best Christmas gift I had ever received. The kindness of a stranger that broke all prejudice(偏见) I may have had of certain types of people. The softness of a human heart can be seen in a simple act. I will never 15 it.