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有一种神奇的蜡烛，点一任你怎么吹也吹不灭，而且看上去和普通的蜡烛一模一样，那么到底是什么玄机能让蜡烛持续燃烧？请你一起参与探究． 查阅资料：普通蜡烛由石蜡和蜡烛芯制成，而吹不灭的蜡烛是在蜡烛芯上包裹一层打火石的粉末，打火石是由某种金属掺入少量稀土元素制成的合金，它的着火点只有150℃，当蜡烛燃烧时，金属并不燃烧；但当蜡烛吹灭后，未冷却的金属接触到氧气就发生燃烧，从而使蜡烛复燃． 老师告诉同学们，蜡烛芯内打火石中的某种金属可能是镁、铜中的一种，为确定该金属的成分，大家设计了以下实验方案，请你填空和回答有关问题（注：不考虑打火石中稀土元素对探究金属性质的影响）． 实验 操作步骤 实验现象 实验结论 1 切开蜡烛，取出打火石，用砂纸打磨 打火石呈银白色 该金属一定不是 ． 2 取少量打磨后的打火石于试管中，滴加稀盐酸 有无色气体产生， 该金属一定不是铁，而是镁 反思交流： （1）实验2中反应的化学方程式为 ． （2）这种蜡烛燃烧时，蜡烛芯里的金属为什么不燃烧？ （3）这种“吹不灭”的蜡烛实际上也可以熄灭，你采用的方法是 ．
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【单选题】People once widely believed that intelligent life existed on Mars. The 19th-century discovery of what appeared to be geometric designs cut across the surface was taken as evidence. The lines were thou...
A.
Because the surface of Mars seemed to be geometric.
B.
Because the lines were drawn across the surface of the planet.
C.
Because a system of canals was thought to be there.
D.
Because it was the Martians that built the canals.
【简答题】(第五章)微晶纤维素常作稀释、黏合和__________三合剂使用。
【单选题】关于风湿性肉芽肿的叙述,下列哪项是错误的?
A.
中心部位多有纤维蛋白
B.
多发生于心肌间质血管旁
C.
特征性细胞是Aschoff细胞
D.
常伴有淋巴细胞、浆细胞浸润
E.
是风湿病的特征性病变，具有诊断意义
【单选题】下列关于风湿性肉芽肿的叙述,哪项错误
A.
中心部位多为纤维蛋白
B.
多发生在心肌间质血管旁
C.
特征性细胞是Aschoff细胞
D.
常伴有淋巴细胞、浆细胞浸润
E.
是风湿病的特征性病变，具有诊断意义
【单选题】Pizza is so old that its origins are not quite clear to historians, but the word pizza comes from the Latin verb pinsere, meaning to press. It may also be related to the Greek word pitta. In any eve...
A.
Space Relationship
B.
Time Sequence
C.
Examples and Illustrations
D.
Compare and Contrast
E.
Cause and Effect
F.
Addition (Enumeration) simple listing
【简答题】阅读理解。 A woman whose sports car was stolen with her dog in it put up notices all over the area that made it clear getting back her pet was more important than her car. 'Whoever did this can keep my car...
【简答题】抄写 并且 翻译 下面的解析(来自考官范文) Chorleywood is a village near London whose population has increased steadily since the middle of the 19th century. The map below shows the development of the village. The map sh...
【简答题】阅读理解。 A woman whose sports car was stolen with her dog in it put up notices all over the area that made it clear getting back her pet was more important than her car. 'Whoever did this can keep my car...
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