2. 外语
  3. 【M1】Most people would describe water like a colorless liquid.【M2】They would know that in very cold conditions it becomes a solid

【M1】Most people would describe water like a colorless liquid.【M2】They would know that in very cold conditions it becomes a solid

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问题     【M1】Most people would describe water like a colorless liquid.【M2】They would know that in very cold conditions it becomes a solid called ice and that when heating on a fire it becomes a vapor called steam.【M3】However, water, they would said, is a liquid.【M4】We have learned that water consists of molecules composed with two atoms of hydrogen and one atom of oxygen, which we describe by the formula H2O.
    【M5】This is equally true of the solid are called ice and the gas called steam.【M6】Chemically there is no difference between the gas, the liquid, and the solid, all of which is made up of molecules with the formula H2O.【M7】This is true of other chemical substances; the most of them can exist as gases or as liquids or as solids.【M8】We may normally think of iron as a solid, but if we will heat it in a furnace, it will melt and become a liquid, and at very high temperatures it will become a gas.【M9】Nothing very permanent occurs when a gas changes a liquid or a solid.【M10】Everyone knows that ice, which has been made by freezing water, can be melted again by warmed and that steam can be condensed on a cold surface to become liquid water.【M11】In fact, it is only because water is so a familiar substance that different names are used for the solid, liquid and gas.【M12】Most substances are only familiar with us in one state,【M13】because the temperatures requiring to turn them into gases are very high, or the temperatures necessary to turn them into solids are so low.【M14】Water is an exceptional in this respect,【M15】which is another reason why its three states have given three different names.
【M2】
选项
答案heating一heated
解析 在时间，条件，让步等状语从句中，当从句主语和主句主语是一致的时候，可以将从句的主语和be的变化形式省略。
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