MPEMBA
EFFECT – SCI & TECH
News:
Mpemba effect: Heat up to
cool down
What's
in the news?
●
The Mpemba effect, named after Tanzanian
student Erasto Mpemba, who brought attention to this counterintuitive
phenomenon in 1969, makes for curious observation.
Mpemba
Effect:
●
The effect is that hot water can freeze faster than cold water in similar conditions.
Recently
Proposed Causes:
1.
Presence of Microbubbles:
●
One of the proposed causes is the presence
of microbubbles that remain suspended in water after boiling.
●
These microbubbles promote convection and
facilitate faster heat transfer. Hence, the warm water cools down more quickly.
2.
Evaporation:
●
As warmer water evaporates more, it takes
away the heat more quickly. Thus, warm water cools down more quickly as
compared to cold water.
3.
Presence of Frost in Cold Water:
●
The presence of frost in cold water acts
as an insulator which impedes/slows down the process of heat loss. This raises
the freezing point of cold water.
4.
Presence of Calcium carbonate and other impurities:
●
Compounds like calcium carbonate
precipitate in warm/hot water and it lowers down the freezing point of warm
water.
●
On the other hand, in cold water, calcium
carbonate and other impurities remain dissolved in the cold water, which
increases the freezing point of cold water.