题干

化学现象中包含发光、发热,许多物质燃烧时都伴随着发光、放热的现象.

小丽认为有发光、放热现象的变化不一定是化学变化,整个学习小组对此展开讨论和验证.

【提出问题】____

【猜想】猜想一:都是化学变化;      猜想二:不一定都是化学变化

【实验】

(1)将干冷的烧杯罩在蜡烛燃烧的火焰上,观察到:a、烧杯内壁上出现水珠;b、手摸烧杯有____ 的感觉;c、蜡烛火焰逐渐变小至熄灭.

分析:蜡烛燃烧生成新物质的名称是____ ,蜡烛燃烧为____变化.

(2)观察白炽灯(灯管为钨丝):a、通电前:灯丝为银白色固体; b、通电中:发出白光,手摸灯泡感觉____ ; c、通电后:灯丝为银白色固体.

灯丝为银白色固体 发出白光,手摸灯泡感觉 灯丝为银白色固体

分析:通电前后,钨丝本身没有发生变化,灯光通电发热、放热属于____ 变化.

【结论】猜想____  (填“一“或”二“)正确.

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答案(点此获取答案解析)

有发光、放热现象的变化都是化学变化吗?,热,水,化学,发热,物理,二

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完形填空

    I had just arrived in this Asian country for a one-year teaching position. One day, I took the subway to visit some ancient palaces and temples in the downtown. The following account of what happened to me has taught me much about culture 1.

    Since all the 2 were taken, I stood. Suddenly, I felt someone pulling on my bag. 3 I probably was in someone's way, I moved over slightly. But in one quick motion(动作), I felt my bag removed from my back, and in a flash it was 4. I turned around to see who the thief was. I looked at the people standing behind me, but didn't see my bag or any 5. My heart sank and I began to 6.

    I glanced around the car only to find directly across from me was an elderly lady, and sitting on her lap was my 7. I tried to get it back from her lap. But as I began to 8 it up, she quickly grabbed(抓住) it back and held onto it. I looked around at the people standing beside me, and those sitting beside her, but no one took any 9 of the situation. Trying not to cause a(an) 10, I tried to negotiate through gestures. I used my hands as best as I could, but she 11 my requests for my bag and pointed to my back. She picked up my bag, showing how 12 it was. I finally began to understand. She was holding my bag to13 me.

    At the next stop, a middle-aged woman got on the crowded subway. Another elderly woman sitting down took her bag, 14 it on her lap. They didn't talk; 15 this older woman was more than pleased to sit with this stranger's bag on her lap throughout her journey.

    As the subway pulled into the main downtown station and I was getting ready to get off, the woman 16 handed me back my bag. But 17 I had a chance to thank her, she had disappeared into the crowd.

    Sadly, this considerate custom was more 18 to me than if I had been robbed. Everyone back home had heard of being robbed—that was 19 city behavior—but having a stranger hold onto someone's bag out of 20, in a city of twelve million people—that was truly unusual.