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主题:【原创】听我来上科学课 -- 月色溶溶

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家园 原来月色忙着上课

我说这几天怎么没看见呢。这个质量守恒,咱也不多说了,先搬wikipedia文摘。

The law of conservation of mass/matter, also known as law of mass/matter conservation, states that the mass of a closed system of substances will remain constant, regardless of the processes acting inside the system. An equivalent statement is that matter cannot be created nor destroyed, although it may change form. This implies that for any chemical process in a closed system, the mass of the reactants must equal the mass of the products. The law of mass/matter conservation may be considered as an approximate physical law that holds only in the classical sense before the advent of special relativity and quantum mechanics.

上面的话,有几点要注意。一是封闭系统。地球质量是否守恒?严格说,不守恒。因为不是封闭系统,天天有石头从天上掉下来。第二个,不要去想相对论和量子力学的东西。这定律在那里不适用。中学课本上说的质量守恒多用在化学反应上,封闭系统内,有多少东西进去,就得有多少东西出来,不然方程式无法配平。三,中学里面还有一个能量守恒。那个是物理题里面解势能,动能,热能转换用的。同样,千万别拉上相对论,量子力学的东西。

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