Question: Why does toast turn black if you burn it

Sarah Montgomery answered on 20 Mar 2025:

The black part of burnt toast is actually unburnt carbon. If you put it into a hot fire (like on a gas stove), it would eventually burn as well and turn into carbon dioxide gas. It’s common when there is a fire for some unburnt material to be left – if you’ve ever seen a bonfire the next day, you may have noticed a pile of ashes still smouldering the next day and gradually reducing in size as the leftover carbon slowly turns into carbon dioxide. This is also a reason why cars need catalytic converters, to make sure all the fuel is fully burnt rather than being released as unburnt particulates.