system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: why does wood when its burning sometimes 'pop' with little sparks?

I'm not exactly sure why it does that. Is there something in the wood?
gpt
It usually occurs because there is a pocket of either water or sap in the wood. This pocket becomes superheated and the pressure builds until it releases explosively (the “pop” you hear). The sparks are little bits of wood that are burning that get knocked off when the pressure releases.