What determines whether something melts or chars/ignites when heated?
In: 5
It depends on how stable the chemical is.
Things that melt remain the same thing as they heat up. Often times, this is because they’re a single element (see: any metal), but also applies to stable compounds (water, for example).
If the compound isn’t stable, it breaks down as it heats up. For example, carbohydrates, even in the absence of anything else, will break down into carbon and water as it heats up. This is charring – “charring” usually specifically involves carbon being left behind; but the same kind of thing can happen even without carbon. For example, heating rust results in pure iron.
Ignition specifically requires a chemical reaction that releases more heat – and often requires access to oxygen or some other thing for the chemical to react with. It’s like charring, except that charring is usually just things breaking down and falling apart, while ignition is things breaking down in a way that releases energy.
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