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除夕的夜晚,烟花在空中绽放,绚丽无比。烟花又称花炮、烟火、焰火,主要用于典礼或表演中。

烟花和爆竹的组成类似,其中都包含黑火药。黑火药由硝酸钾、木炭和硫粉混合而成,遇火或者强烈撞击等条件下则会发生剧烈反应,瞬间产生大量由二氧化碳、氮气、二氧化硫等组成的混合气体,同时释放大量热。由于气体体积急剧膨胀,压力猛烈增大,于是发生爆炸。

制作烟花的过程中,还加入一些发光剂和发色剂,它们使烟花呈现五彩缤纷的颜色。发光剂是金属镁或金属铝的粉末。发色剂是一些金属化合物,不同金属元素的化合物在火焰上灼烧时,发出不同颜色的光芒。例如,氯化钠和硫酸钠等物质在火焰上灼烧时会发出黄色光芒;含钙化合物会发出砖红色光芒;含铜化合物会发出绿色光芒。因此,人们常通过燃放烟花来烘托节日气氛,但由于黑火药燃烧会产生有害气体,也带来一些环境问题。

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    New Year's resolutions(决心)have been around long enough that we all scent to stick to the same ones--hit the gym, lay off the candy, read more books, call your mother-regardless of whether we follow through with our intentions.

    While January 1st seems like the perfect time to have a new start again, exactly when people developed that mindset(思维模式)isn't common knowledge. It turns out that the modern belief of' a New Year's resolution isn't as old as you thought. According to many historians, the ancient Babylonians were the first group of people to make New Year's resolutions. However, instead of making a commitment to self improvement, they made a commitment to the gods to pay their debts and return any objects they had borrowed.

    An ancient Roman tradition from 46 B. C, bears even more likeness to modern resolutions. Emperor Julius Caesar declared January the month of Janus. Romans believed Janus looked backwards into the previous year and ahead into the future. In his honor, they made sacrifices to the god and promises of good behavior for the coining year.

    But the modern New Year's resolution didn't fully form until centuries later. The practice was common enough by the early 1800s. An article in 1802 states, "Statesmen have sworn to have no other objet in view than the good of their country. the physicians have determined to advise the use of medicine no more than is necessary, and to the very reasonable in their fees.”

    The first time “New Year's resolution" appeared as a phrase was in the January 1st issue of a Boston newspaper in 1813. “I believe there are a lot of people," the article goes, “with a serious determination of beginning the New Year with new resolutions and new behavior, and with the full belief that they shall accept punishment for all their former faults and wipe them away.

    So as you make (and possibly fail at) your New year's resolutions, know that you're in good company.