题干

甲烷、乙醇和氢气都是常见的燃料.

(1)上述三种物质中,属于化石燃料的是____ .

(2)乙醇的化学式为____ .

(3)将甲烷点燃,用一只冷而干燥的烧杯罩在火焰上方,可以观察到烧杯壁上有水珠生成,由此可证明甲烷中含有____ 元素.甲烷完全燃烧的化学反应方程式为____ .

(4)使用氢气作燃料最突出的优点是(用化学方程式表示)____ .

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答案(点此获取答案解析)

甲烷,C2H5OH,氢,CH4+2O2CO2+2H2O,2H2+O22H2O

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The spirits of giving

    Two weeks before Christmas, two girls were walking down the street, laughing on some ice that remained from a recent snow. Merrily they shared what they hoped to 1from Christmas.

    They stopped to talk to an old man named Harry, who was on his knees2weeds around a large oak tree. He wore a pair of 3garden gloves. His fingers were sticking out of the ends, blue from the4.

    Harry told them he was getting the yard in 5as a Christmas gift for his mother, who had died several years before. He said with his eyes 6with tears,"My mother was all I had. She loved her7and her trees, so I do this for her at Christmas."

    His words8the girls and soon they were down on their hands and knees helping him 9around the trees. When they were finished, Harry pressed a quarter into each of their hands and said, "I wish I could 10 you more, but it's all I've got right now."

    The girls had often passed his house, and as they 11 on they remembered that the house was always12. No decorations to add cheerfulness were anywhere in sight. Harry sat behind curtain windows, looking 13.

    The quarter in one little girl's palm(手心) seemed to burn a hole of guilt 14 they walked on. The next day she called her friend and they 15 to put their quarters in a jar marked "Harry's Christmas Present". Then they began to seek out small jobs to16more. Every nickel, dime and quarter they earned went into the jar.

    Two days before Christmas, they had enough money to buy new 17and a card. Christmas Eve found them18Harry's doorstep singing carols(圣诞颂歌). When Harry opened the door, they presented him with the gloves wrapped in pretty paper and a19pumpkin pie a mother had just baked. With 20hands he tore open the paper from the gloves, and then to their surprise, he held them to his face and wept.