题干

有人说:“化学变化时一般伴随着发光、放热、颜色变化、气体产生、生成沉淀等,这些现象只能帮助我们判断是否是化学变化,却不能作为判断是否是化学变化的依据”.对此说法你认为正确吗?谈一谈你的观点.

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答案(点此获取答案解析)

解:有新物质生成的变化属于化学变化.化学变化中常常伴随着发光、放热、有颜色变化、有沉淀出现等现象.这些现象只能帮助人们认识化学变化,但是不能作为判断化学变化的依据.如电灯发光、发热属于物理变化;判断化学变化的唯一依据是变化过程中是否有新物质生成.

答案:正确;新物质生成的变化属于化学变化.化学变化中常常伴随着发光、放热、有颜色变化、有沉淀出现等现象.这些现象只能帮助人们认识化学变化,但是不能作为判断化学变化的依据.如电灯发光、发热属于物理变化;判断化学变化的唯一依据是变化过程中是否有新物

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Big City Bus Driver

    When I was 20, I went to stay with a friend for two weeks in Vancouver. My friend worked during the day, so I decided to go 1 on my own. I knew where I was and where I wanted to go, the Vancouver Aquarium (温哥华水族馆). It sounded 2.

    But soon I was completed 3 I boarded a bus, figuring it must do a circle, right? I rode a good half hour before becoming impatient and then got 4 I walked quite a while, up and down various blocks, but had no idea where I was.

    I've lived in a tiny town all my life, rarely leaving it. Being a “small town girl”, I admit I'm fairly 5about city life. People at home always told me city people were cold and unconcerned about others, so I was afraid to 6to anyone.

    I got on another bus, and then another again. Finally, after hours, I decided to get on ONE bus, and stay on 7 I recognized something. I rode over half an hour. Nothing ever seemed 8 When I became the only passenger on the bus, I began to get 9 I had no cellphone, and didn't even10 my friend's office telephone number.

    As I was about to give up and leave the bus, the driver asked11 I wanted to go. I told him the aquarium, and he laughed, saying his bus wouldn't go anywhere near. I12 back in my seat, really afraid and upset. He asked where I was from, and I told him what had happened and now I just wanted to go back to my friend's place.

    13, the driver pulled the bus over and called me to the front. He gave me detailed 14 as to which buses to take, and how to understand the bus system. He 15 printed the bus tickets I needed from his machine.

    I was shocked. He spent a good twenty minutes 16 me, telling me everything I needed to know, before giving me the tickets. I thanked him repeatedly, and asked him how much I 17 for the tickets. “Nothing. Just get yourself to your friend's home.”

    Thanks to his 18 I was able to make my way back to my friend's house. I don't know what I would have done if that driver had not taken the 19 to help me. What people had told me was not true. City people 20 just like the driver. I never did learn his name, but I'll always remember him.