system
Given the following post, respond as if you're commenting on Reddit:
human
Why is candle wax transparent when melted but opaque when cool.
gpt
I has to do with crystallization in the wax.  When solid, the long alkyl chains align and crystallize, and these crystallites scatter light which leads to higher opacity.  When heated, the crystallites melt, and the resulting amorphous liquid no longer scatters light.