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    【化学变化和物理变化】 常见的物理变化

    时间:2018-12-28 03:27:48 来源:柠檬阅读网 本文已影响 柠檬阅读网手机站

      There are two kinds of changes-chemical change and physical change   In a chemical change, there is always a new substance (物质) formed(生成). Breaking up water into hydrogen (氢气)and oxygen (氧气) is a chemical change. In each of the chemical change, at least one new sub-stance is formed. A change is not a chemical change if it doesn"t form a new substance.
      Physical changes are very common, too. There are many examples. You can make a physical change by tearing(撕)a piece of paper in two, or by cutting a piece of iron with a lathe (车床). Here paper is still paper, and the iron is still iron.
      Another way of making physical change is dissolving(溶解)something in water. When you dissolve salt in water,the salt disappears,You may think that a new substance has been formed.But really there is no new substance. The salt is still salt. You can stil taste it. So the dissolving of anything is a physical change.
       When water freezes(结冰), the change is also a physical one. The water may change from a liquid (液体) to a solid (固体), but it is still the same substance. That is why the freezing of anything is a physial change.

    相关热词搜索: 物理变化 化学变化

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