The initial stage in a phase transformation. It is evidenced by the formation of small particles (nuclei) of the new phase, which are capable of growing.
The process of providing sites for:
- new bubbles to form in a liquid that is boiling or supersaturated with gas
- new droplets to condense from a supersaturated vapour
- new crystals to form in a supersaturated solution. Nucleation sites can be scratches in a surface, dust particles, seed crystals, and so on.