十万个为什么·科学启蒙30篇（2）
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What Makes Popcorn Pop?
爆米花为什么会爆开？
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Popcorn kernels contain a small amount of water sealed inside a hard, moisture-proof hull — usually about 13–14% by weight.
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When heated, the water turns to steam and builds pressure inside the kernel until the hull ruptures at around 175°C and 9 atmospheres.
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The sudden release of steam causes the starchy interior to expand rapidly, cool, and solidify into the fluffy white shape we recognize.
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Only certain corn varieties pop well because their hulls are strong enough to hold pressure but thin enough to burst cleanly.
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Kernels that don’t pop — called 'old maids' — either lost moisture over time or have tiny cracks letting steam escape slowly.
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Microwave popcorn works because the bag traps steam and heat, but overheating can burn kernels or release harmful fumes from artificial flavorings.
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Ancient civilizations in Peru and Mexico cultivated popcorn over 7,000 years ago, long before modern cooking methods existed.
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Each kernel pops with a small 'explosion' that produces a distinctive snap — audible up to 3 meters away in quiet conditions.