Can hot water actually freeze faster than cold water, or is it a myth?
In short: For over 2,500 years, thinkers from Aristotle to modern physicists have debated whether hot water freezes faster than cold. Known as the Mpemba effect, this counterintuitive phenomenon has sparked intense scientific disagreement, with some researchers proposing complex molecular theories while others insist that basic thermodynamics makes the idea impossible.
The mystery of the Mpemba effect is named after Erasto Mpemba, a Tanzanian student who noticed in 1963 that his warm ice cream mixture froze faster than a cooler one. While the observation has been debated since the time of Aristotle, Rene Descartes, and Francis Bacon, it remains a subject of contention. Some experts argue that hot water can indeed freeze faster, while others, such as Prakash Govindan of MIT, maintain that hot water must logically take longer because it must first lose more energy to reach the freezing point of 0°C.
Proposed explanations for the effect vary wildly. In 2013, the Royal Society of Chemistry awarded a prize to a researcher who suggested that convection currents in warm water might accelerate cooling. Another theory from physicists at Nanyang Technological University in Singapore focuses on molecular bonding. They argue that as water warms, hydrogen bonds stretch, allowing covalent bonds to store and then release energy, potentially facilitating a faster freeze. However, this theory has not yet been peer-reviewed.
Skeptics argue that the effect is often misunderstood or influenced by external variables. Govindan notes that while a freezer may initially extract heat faster from a hot container due to a greater temperature difference, the water still must reach the same state as the cold sample. Factors like dissolved gases, impurities, or the specific composition of ice cream mixtures may influence results, but there is no consensus that hot water inherently defies standard thermodynamic principles. Ultimately, whether the Mpemba effect is a genuine physical anomaly or a result of experimental conditions remains an open question.
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Sources
- Summary by Intellect · source: How Can Hot Water Freeze Faster Than Cold Water?
- Also: Does hot water freeze faster than cold water?
- Also: www.scientificamerican.com — Does Hot Water Really Freeze Faster Than Cold Water?
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