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Freezing Speed of Hot Versus Cold Water
bostonman:
Recently we had single digit temperatures approaching and decided to experiment with the freezing speed of hot versus cold water.
From research, hot water should freeze faster, but I didn't exactly get these results.
The outside temperature was approximately 20-25 degrees F (and deceasing slowly). I placed a piece of plywood across two sawhorses (to eliminate the ground from acting as a heat sink), placed two identical cookie tins on the plywood (spaced apart), used a piece of copper tape to hold the temperature probe on the bottom of each pan (I used two identical temperature data loggers), and, simultaneously poured tap water in one, and near boiling water in the other.
If my understanding of thermodynamics is correct, large delta temperatures will cool quickly and then slower as it gets closer to the ambient air (I believe technically they will never be exact). As an example, if I heated a steal block so it was glowing red, and placed it outside in 0 degrees F, it will cool very quickly in the beginning, and then slower and slower until it almost reaches 0 degrees F.
Having said this, if you look at my hot versus cold graph, the hot water seems to do just that. Leaving out the fine details such as just exactly what is going on with the molecules, from research, I expected the hot to freeze noticeably faster.
Looking at the zoomed in graph around 32 degrees F, the hot water technically froze before the cold, but technically they appear to have froze almost at the same time.
The temperature data loggers have a +/- of about 1.5 or 2 degrees (I don't have the specs at the moment).
Ignoring the error in the data logger and other differences, it seems very little difference exists between freezing hot water versus cold water. Also, I'll add that both cookie tins had a high amount of ice indicating the temperature was truly 32 - and they were both ice at near the same time.
Am I thinking of this wrong, or does the two technically freeze within a short time of each other and technically the hot beats cold but by a very irrelevant amount?
bdunham7:
Did you weigh the water in each? :)
bostonman:
Basically the same amount of water in each.
Both tins were filled to the same height.
emece67:
.
strawberry:
http://hyperphysics.phy-astr.gsu.edu/hbase/Kinetic/vappre.html
what does F mean?
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