system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 why does sugar turn brown when melted?
gpt
Sugar is a molecule made of a particular arrangement of carbon, oxygen, and hydrogen atoms.  When you heat up the sugar, this adds energy to the system that can be used to fuel chemical reactions that rearrange the bonds between these atoms.  Some of these compounds are dark brown in color and add caramel flavors to the sugar.  Similar reactions occur in meat when you cook it and get a tasty brown crust.