* Solid butter has a more tightly packed structure. The molecules are held in a regular, crystalline arrangement.
* Liquid butter has a less dense structure. The molecules are more spread out and can move more freely.
Therefore, when butter melts, it expands slightly, meaning its volume increases.
However, the change in volume is usually quite small and not very noticeable. It's more significant when comparing butter in its solid and liquid states than during the melting process itself.
