正在确认阅读权限…
Why Does Ice Float on Water?
冰为什么能浮在水面上
精读先不看文字，完整听一遍。
-
Ice floats because it is about 9% less dense than liquid water—a rare property among substances.冰能浮在水面上，是因为其密度比液态水低约9%——这在物质中极为罕见。
-
When water cools below 4°C, its molecules begin forming open hexagonal crystals held by hydrogen bonds.当水温降至4°C以下时，水分子开始通过氢键形成疏松的六边形晶体结构。
-
These crystals leave empty spaces between molecules, making solid ice take up more volume than the same mass of water.这些晶体结构使分子间留有空隙，导致同等质量的固态冰体积大于液态水。
-
That lower density means ice weighs less per liter than water, so it rises instead of sinking.密度降低意味着每升冰的质量小于水，因此冰会上浮而非下沉。
-
If ice sank, lakes and oceans would freeze from the bottom up, killing most aquatic life each winter.倘若冰会下沉，湖泊与海洋将自底部向上冻结，每年冬季都会杀死大部分水生生物。
-
This unique behavior also causes pipes to burst when water freezes inside them—expanding outward with great force.这种独特性质还会导致水管内结冰时向外剧烈膨胀，从而胀裂管道。
-
Water reaches its maximum density at 4°C, which is why deeper lake water stays near that temperature year-round.水在4°C时密度最大，因此深湖底层水温常年维持在此温度附近。
-
Antarctic ice shelves float because they’re connected to land-based glaciers but extend over seawater.南极冰架之所以能漂浮，是因为它们与陆上冰川相连，却延伸至海面之上。
-
Scientists study ice density to understand climate patterns, since melting sea ice doesn’t raise sea level—but land ice does.科学家通过研究冰的密度来理解气候模式，因为海冰融化不会推高海平面，而陆冰融化会。
-
No other common substance expands when freezing; most solids sink in their own melted form.除水外，其他常见物质凝固时均收缩；绝大多数固体在其熔融态中会下沉。
精读 · 大约 10 分钟
听 → 读 → 学表达 → 懂 → 今天会说这一句 → 跟读录音 → 自己说一句。
③ 学 · 重点表达
- Antarctic ice shelves float because they’re connected to land-based glaciers but extend over seawater. 南极冰架之所以能漂浮，是因为它们与陆上冰川相连，却延伸至海面之上。
- No other common substance expands when freezing; most solids sink in their own melted form. 除水外，其他常见物质凝固时均收缩；绝大多数固体在其熔融态中会下沉。
- Ice floats because it is about 9% less dense than liquid water—a rare property among substances. 冰能浮在水面上，是因为其密度比液态水低约9%——这在物质中极为罕见。
④ 懂 · 选一选
⑤ 今天会说这一句
Antarctic ice shelves float because they’re connected to land-based glaciers but extend over seawater.
⑥ 跟读并录音
Antarctic ice shelves float because they’re connected to land-based glaciers but extend over seawater.
第一版：录下来、回听、再听标准音。系统打分以后再加。
⑦ 说 · 自己来一句
用今天的表达，自己说一句。
例子：Antarctic ice shelves float because they’re connected to land-based glaciers but extend over seawater.
已记下。连续天数以后会显示在课表里。
陈老师指导
课程开发中，敬请期待。成人和孩子都可以先自学听读、精读。
这边的讲解音轨还在做。想先跟着老师走完固定 30 课，可以去陈老师带读社（和自学通行不是同一份会员）。
课程开发中，敬请期待。