十万个为什么·科学启蒙30篇（3）

10 / 30

火焰为什么通常是橙色的

An orange flame appears when tiny hot particles of carbon—called soot—glow in the heat like tiny lightbulbs.
This type of incandescence happens in incomplete combustion, where fuel doesn’t burn fully due to limited oxygen.
Candles, wood fires, and gas stoves on low settings all produce such warm-colored flames.
Blue flames, in contrast, come from complete combustion and emit light mostly from excited gas molecules.
The temperature of an orange flame ranges from about 1,000°C to 1,200°C—hot, but cooler than blue ones.
Sodium in salt or food splatters adds a stronger yellow-orange hue because sodium atoms glow brightly at that wavelength.
A candle’s wick draws melted wax upward, where capillary action feeds vaporized fuel into the flame zone.
If you restrict airflow to a Bunsen burner, its blue flame turns orange and flickers more wildly.
Firefighters watch flame color carefully: orange suggests smoldering materials, while blue hints at gas leaks.
Even the Sun’s visible surface glows orange-yellow—not from soot, but because its 5,500°C surface emits peak light in that range.