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例1(2008年湛江中考题)小明同学在研究某气体(纯净物)的性质时做了如下实验:将铜丝绕成螺旋状放在酒精灯火焰上灼烧,铜丝表面由光亮的红色变为黑色;趁热将表面变黑的铜丝伸入到盛有这种气体的试管中,观察到铜丝表面的黑色又变为光亮的红色。
Example 1 (2008 Zhanjiang examination question) Xiaoming’s student did the following experiment when he was studying the properties of a gas (purity): The copper wire was wound spirally on the flame of an alcohol lamp and the surface of the copper wire was bright red. It turned black; when the black copper wire was put into the test tube containing this gas, the black color on the surface of the copper wire was changed to bright red.