冬季可用煤炉取暖，分析下列做法或现象中的原理．
（1）生煤炉时，需先引燃木材．
（2）开始时煤燃烧较弱，过一会变得剧烈．
（3）煤层上方有时会出现蓝色火焰．
（4）用扇子扇炉火，越扇越旺．
（1）木材燃烧放出热量，煤吸收热量后温度升高，当温度达到煤的着火点时，煤就燃烧起来．
（2）燃烧放热，使周围的煤达到着火点，燃烧旺盛．
（3）燃烧产生的二氧化碳被热的碳还原生成一氧化碳，一氧化碳燃烧能够发出蓝色火焰．
（4）增加空气量，从而使煤与氧气的接触面积增大，促进煤的燃烧．
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| Nick is my pen pal. He is 12 years old. He is from Canada. He lives in Ottawa. He speaks English and French. His favourite subject is science. He likes Chinese, too. And he says he can speak a little Chinese, but he can't write in Chinese. Nick likes sports, too. He likes swimming best. He goes swimming on weekends with his father. He says he can swim very well. He doesn't like Physics. He thinks it is too difficult. Nick has a big family. There are eight people in his family, his grandpa, grandma, father, mother and his brothers and sisters. He has two brothers and two sisters. They are Bob, Tim, Jane and Susan. They are happy!
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