Mpemba Effect &

Mpemba Effect & "Amateur" Science

BY : Rhiannon Nevinczenko

A high school student once asked his teacher, "If you take two similar containers with equal volumes of water, one at 35 °C (95 °F) and the other at 100 °C (212 °F), and put them into a freezer, the one that started at 100 °C (212 °F) freezes first. Why?"
Instead of an answer, the student received ridicule from his teacher and classmates alike. However, his teacher later performed experiments that confirmed his student's question. The pair published a paper on the discovery together in 1969, and the effect was named the Mpemba effect, after the student Erasto Mpemba. Mpemba became a scientist in his adulthood.
Though it wasn't named until this event, the Mpemba effect has been known to humankind for much longer. Aristotle, Francis Bacon, René Descartes, and Joseph Black have all been recorded as commenting on the phenomenon of hot water freezing more readily than cold water.
Multiple explanations for the Mpemba effect have been proposed. Disputes over the explanation continue to this day. Some possible explanations include: Convection, microbubble-induced heat transfer, crystallization, frost insulation, the influence of solutes, hydrogen bonding, thermal conductivity, distribution function, dissolved gases, and evaporation.
You are never too young to make an important observation, and ultimately contribute to scientific knowledge!
Image credit: Alfredo Ristol via Flickr. CC BY 2.0.

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