Mpemba Effect

Context: Indian scientists have developed the first supercomputer-powered simulation that successfully captures the Mpemba effect, resolving a long-standing scientific paradox of hot water freezing faster than cold.

About Mpemba Effect:

What it is?

• The Mpemba effect refers to the counterintuitive phenomenon where hot water freezes faster than cold water under specific experimental conditions.
• Named after Erasto Mpemba, a Tanzanian student who reported it scientifically in 1969, though it was noted earlier by Aristotle, Bacon, and Descartes.

How it works?

• The Mpemba effect occurs because water’s behaviour is shaped by more than just its temperature. When water is heated, its physical and molecular state changes, which can influence how it freezes later.
  • Evaporation: Hot water loses some mass as vapour, so less water remains to freeze, speeding up the process.
  • Dissolved gases: Heating drives out dissolved gases, subtly changing the water’s freezing characteristics.
  • Convection currents: Temperature gradients in hot water create internal circulation that enhances heat loss.
  • Supercooling: Hot water may begin freezing at a higher temperature than cold water, allowing it to solidify sooner.
  • Environmental effects: Hot containers can alter their surroundings, improving overall cooling efficiency.
• Since these factors vary with conditions, no single mechanism explains the effect universally; different processes dominate in different situations.

Applications:

• Advances understanding of non-equilibrium physics and phase transitions.
• Improves climate and cryosphere modelling, including ice formation processes.
• Relevant to industrial freezing, food processing, and materials science.
• Demonstrates the power of supercomputing in resolving classical scientific paradoxes.