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Why Does Ice Float—And Why Is That So Important for Life?
为什么冰能浮在水面上？这对生命有多重要？
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Ice floats because water expands when it freezes, becoming about 9% less dense than liquid water.
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This unusual behavior results from hydrogen bonds arranging into open hexagonal lattices as temperature drops.
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Most substances contract and sink when solidifying, but water’s density peaks at 4°C before decreasing.
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Floating ice forms an insulating layer that protects aquatic life beneath from complete freezing.
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Without this property, lakes and oceans would freeze solid from the bottom up, killing most ecosystems.
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Seasonal ice cover also regulates global climate by reflecting sunlight back into space.
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Polar bears, seals, and algae all depend on stable sea ice platforms for hunting and reproduction.
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Glaciers move slowly because basal ice melts under pressure, lubricating their slide over bedrock.
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Engineers mimic ice’s low-density structure to design lightweight, strong aerogel materials.
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If water behaved like most liquids, Earth might never have developed complex multicellular life.