Nucleation Definition (Chemistry and Physics)

What the Nucleation Process Is

Crystals grow by nucleation of atoms or molecules to form organized structures.
Crystals grow by nucleation of atoms or molecules to form organized structures. WIN-Initiative/Neleman / Getty Images

Nucleation Definition

Nucleation is the process where droplets of liquid can condense from a vapor, or bubbles of gas can form in a boiling liquid. Nucleation can also occur in crystal solution to grow new crystals. It is seen in gases when tiny bubbles coalesce into larger ones. In general, nucleation is a self-organizing process that leads to a new thermodynamic phase or a self-assembled structure.

Nucleation is affected by the level of impurities in a system, which can provide surfaces to support assembly. In heterogeneous nucleation, organization begins at nucleation points on surfaces. In homogeneous nucleation, organization occurs away from a surface. For example, sugar crystals growing on a string is an example of heterogeneous nucleation. Another example is the crystallization of a snowflake around a dust particle. An example of homogeneous nucleation is growth of crystals in a solution rather than a container wall.

Examples of Nucleation

  • Dust and pollutants provide nucleation sites for water vapor in the atmosphere to form clouds.
  • Seed crystals provide nucleation sites for crystal growing.
  • In the Diet Coke and Mentos eruption, the Mentos candies offer nucleation sites for the formation of carbon dioxide bubbles.
  • If you place your finger in a glass of soda, carbon dioxide bubbles will nucleate around it.
Carbon dioxide bubbles nucleating on a finger.
Carbon dioxide bubbles nucleating on a finger. Arie Melamed-Katz

Sources

  • Pruppacher, H. R.; Klett J. D. (1997). Microphysics of Clouds and Precipitation.
  • Sear, R.P. (2007). "Nucleation: theory and applications to protein solutions and colloidal suspensions" (PDF). Journal of Physics: Condensed Matter. 19 (3): 033101. doi:10.1088/0953-8984/19/3/033101