教育部重点推荐学科网站

帮助中心
微信登录，您好！【】有效期： 0天 　资金余额： 元
  • 会员中心 | 退出登录
  • 资金余额： 元
  • 可用：
  • 经验积分： 分
  • 待阅短信： 条
  • 待签文章： 篇
  • 登录次数： 次

当前位置：首页 > 教学参考> 学生园地> 趣味物理 > 内容详情

教学参考

假如“水”总是“热胀冷缩”，后果会多么可怕！

作者：佚名  人气： 685 次  时间：2018年08月25日  星级：

中学物理曾经告诉我们所有人一个常识，一般物质都遵循“热胀冷缩”这一物理规律。

可是，“水”却是个另类奇葩。

水在4°C以上时的确是遵循“热胀冷缩”规律的。

可是在0°C~4°C却遵守“热缩冷胀”规律。因此水在4°C时体积最小，密度最大。

我们把水的这个特性叫做“反常膨胀”！

先举个初中物理常考的例子：冬天自来水管被冻裂的物理原因——一是根据水的反常膨胀原理，水凝固成冰时体积会增大；二是金属水管遵循热胀冷缩规律，在温度降低时，体积会收缩。里面变大，外面变小，当然要裂开。

接下来，我们讨论一下“水"的物理规律。

【1】4°C以上的水——热胀冷缩！

我们知道，自然界的水总是先从表面开始冷却的，表面水温总是低于下面的水温。那么，当4°C以上的水从高于4°C的温度向4°C降低的过程中，由于是正常的热胀冷缩，所以上层的水密度会大于下层的水的密度，于是上层水下沉，下层水上升，从而形成对流，整个水体会很快达到相同的温度！

【2】0°C~4°C的水——热缩冷胀！

当水温从4°C向0°C降低的过程中，由于热缩冷胀，所以上层水的密度小于下层水的密度，不会再下沉！下层的水也不会再上升，于是没有了对流现象，水的温度不再均匀。当表面的水结冰后，冰与水混合物温度为0°C，于是，从表面到底部水温逐渐升高，由于4°C水的密度最大，因此河底的水温为4°C，水中的各种生物会安全生存。

我们可以知道结果了——假如没有水的反常膨胀，那么当水温从4°C向0°C降低的过程中——整个水体会达到相同的0°C，最终会全部结成冰！于是所有的生物都会被“冻住”！

如果真的这样，地球上的生命就不可能进化，人类也不可能诞生了！

似乎这一物理特性就是为了生物以及人类的产生而特意设定的物理奇迹！ 

用户评论

(以下评论仅代表网友意见，与本站立场无关)

网友评论共 0 条
[{"id":136,"name":"电子课本","url":"/wlzx/List_136.html","target":"_self",children: [{"id":137,"name":"人教版课本","url":"/wlzx/List_137.html","target":"_self",children: [{"id":140,"name":"人教八年级上册","url":"/wlzx/List_140.html","target":"_self"},{"id":141,"name":"人教八年级下册","url":"/wlzx/List_141.html","target":"_self"},{"id":142,"name":"人教九年级全册","url":"/wlzx/List_142.html","target":"_self"}] },{"id":138,"name":"沪科版课本","url":"/wlzx/List_138.html","target":"_self",children: [{"id":143,"name":"沪科八年级全册","url":"/wlzx/List_143.html","target":"_self"},{"id":144,"name":"沪科九年级全册","url":"/wlzx/List_144.html","target":"_self"}] },{"id":139,"name":"苏科版课本","url":"/wlzx/List_139.html","target":"_self",children: [{"id":160,"name":"新苏科版八年级上册","url":"/wlzx/List_160.html","target":"_self"},{"id":179,"name":"新苏科版八年级下册","url":"/wlzx/List_179.html","target":"_self"},{"id":185,"name":"新苏科版九年级上册","url":"/wlzx/List_185.html","target":"_self"},{"id":186,"name":"新苏科版九年级下册","url":"/wlzx/List_186.html","target":"_self"}] },{"id":145,"name":"沪粤版课本","url":"/wlzx/List_145.html","target":"_self",children: [{"id":154,"name":"新沪粤八年级上","url":"/wlzx/List_154.html","target":"_self"},{"id":155,"name":"新沪粤八年级下","url":"/wlzx/List_155.html","target":"_self"},{"id":159,"name":"新沪粤九年级上","url":"/wlzx/List_159.html","target":"_self"},{"id":162,"name":"新沪粤九年级下","url":"/wlzx/List_162.html","target":"_self"},{"id":146,"name":"沪粤八年级上册","url":"/wlzx/List_146.html","target":"_self"},{"id":147,"name":"沪粤八年级下册","url":"/wlzx/List_147.html","target":"_self"},{"id":148,"name":"沪粤九年级上册","url":"/wlzx/List_148.html","target":"_self"},{"id":149,"name":"沪粤九年级下册","url":"/wlzx/List_149.html","target":"_self"}] },{"id":150,"name":"北师大版课本","url":"/wlzx/List_150.html","target":"_self",children: [{"id":151,"name":"北师大版八年级上册","url":"/wlzx/List_151.html","target":"_self"},{"id":152,"name":"北师大版八年级下册","url":"/wlzx/List_152.html","target":"_self"},{"id":153,"name":"北师大版九年级","url":"/wlzx/List_153.html","target":"_self"}] },{"id":180,"name":"教科版电子课本","url":"/wlzx/List_180.html","target":"_self",children: [{"id":181,"name":"教科版八年级上册","url":"/wlzx/List_181.html","target":"_self"},{"id":182,"name":"教科版八年级下册","url":"/wlzx/List_182.html","target":"_self"},{"id":183,"name":"教科版九年级上册","url":"/wlzx/List_183.html","target":"_self"},{"id":184,"name":"教科版九年级下册","url":"/wlzx/List_184.html","target":"_self"}] },{"id":187,"name":"上教版电子课本","url":"/wlzx/List_187.html","target":"_self",children: [{"id":188,"name":"上教版八年级上册课本","url":"/wlzx/List_188.html","target":"_self"},{"id":193,"name":"上教版八年级下册课本","url":"/wlzx/List_193.html","target":"_self"},{"id":189,"name":"上教版九年级上册课本","url":"/wlzx/List_189.html","target":"_self"},{"id":194,"name":"上教版九年级下册课本","url":"/wlzx/List_194.html","target":"_self"}] }] },{"id":1277,"name":"考试大纲","url":"/wlzx/List_1277.html","target":"_self",children: [{"id":1403,"name":"中考大纲","url":"/wlzx/List_1403.html","target":"_self"},{"id":1404,"name":"课程标准","url":"/wlzx/List_1404.html","target":"_self"}] },{"id":1278,"name":"教学研究","url":"/wlzx/List_1278.html","target":"_self",children: [{"id":1405,"name":"教学论文","url":"/wlzx/List_1405.html","target":"_self"},{"id":1406,"name":"课题研究","url":"/wlzx/List_1406.html","target":"_self"}] },{"id":1279,"name":"备课参考","url":"/wlzx/List_1279.html","target":"_self",children: [{"id":1407,"name":"参考资料","url":"/wlzx/List_1407.html","target":"_self",children: [{"id":27,"name":"声学参考资料","url":"/wlzx/List_27.html","target":"_self"},{"id":26,"name":"光学参考资料","url":"/wlzx/List_26.html","target":"_self"},{"id":28,"name":"热学参考资料","url":"/wlzx/List_28.html","target":"_self"},{"id":24,"name":"力学参考资料","url":"/wlzx/List_24.html","target":"_self"},{"id":25,"name":"电磁学参考资料","url":"/wlzx/List_25.html","target":"_self"},{"id":29,"name":"综合知识资料库","url":"/wlzx/List_29.html","target":"_self"}] },{"id":1408,"name":"物理图库","url":"/wlzx/List_1408.html","target":"_self",children: [{"id":62,"name":"声热学图片","url":"/wlzx/List_62.html","target":"_self"},{"id":61,"name":"光学图片","url":"/wlzx/List_61.html","target":"_self"},{"id":60,"name":"电磁学图片","url":"/wlzx/List_60.html","target":"_self"},{"id":59,"name":"力学图片","url":"/wlzx/List_59.html","target":"_self"}] }] },{"id":1280,"name":"实验探究","url":"/wlzx/List_1280.html","target":"_self",children: [{"id":1409,"name":"科学探究","url":"/wlzx/List_1409.html","target":"_self"},{"id":1410,"name":"物理实验室","url":"/wlzx/List_1410.html","target":"_self"}] },{"id":1281,"name":"物理广角","url":"/wlzx/List_1281.html","target":"_self",children: [{"id":1411,"name":"物理前沿","url":"/wlzx/List_1411.html","target":"_self"},{"id":1412,"name":"物理学家","url":"/wlzx/List_1412.html","target":"_self"}] },{"id":1282,"name":"学生园地","url":"/wlzx/List_1282.html","target":"_self",children: [{"id":1413,"name":"趣味物理","url":"/wlzx/List_1413.html","target":"_self"},{"id":1414,"name":"生活科普","url":"/wlzx/List_1414.html","target":"_self"},{"id":1416,"name":"学习指导","url":"/wlzx/List_1416.html","target":"_self"}] }]