為什麼結冰的水（冰塊）會浮在水面上，而多數物質的固態會比液態重？ Why does ice float on water, whereas for most substances, the solid state is denser than the liquid state?
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水分子在結冰時形成疏鬆的氫鍵晶體結構，導致體積膨脹、密度變小 Water molecules form a loose hydrogen-bonded crystal structure upon freezing, causing the volume to expand and density to decrease 水在 4°C 時密度最大，結冰時水分子排列成網狀晶體，使體積增加約 9%，因此密度小於水而能浮在水面上。 Correct! Water has maximum density at 4°C. When freezing, water molecules arrange into an open crystal lattice, increasing volume by about 9% and making it less dense than liquid water.