Quite often throughout the years, many people have come up with their own theories about what freezes quicker, hot water or cold water. "Well I saw in Reader's Digest ...", one says. "Oh, but the Home Living magazine said ...", quotes another. "Well I heard from someone who's taking chemistry that ...", dominantly states another participant.
No matter what theory presents itself, I find myself always repeating. "No matter what, before water can freeze, it must reach a temperature near 0 degrees Celsius!" To which my statement is invariably rebuked, "But I tested in my freezer ..."
Now, I commend anyone who runs home experiments! Right on!!! They are fun and get you in the habit of recording information. Now, if you do the freezer test, you must make sure that "All things are equal". This means that, the freezer must have an even temperature, not one side warmer then the other (should you place the trays away from each other) Make sure your trays are identical and make sure that whatever you lay them on top, is identical as well. Preferably, just the plastic base of the freezer. Also, do not open the freezer door ever 5 minutes!! This will ruin the experiment. If you can't figure out why, then bother with it and start reading a grade 8 chemistry book.
Now .. moving on :) There are specific circumstances where hot water WILL freeze quicker then cold water. One, if the water is near or at boiling, evaporation will help. Why? 1. A high amount (let's say 'y') of calories will be spent evaporating a certain weight of water. Say 1 gram for measurement purposes. Spending all this energy will cool the water down quickly. Moreover, evaporation will mean that there is less water to freeze. 2. If you have something of equal mass under the tray - say another tray of frozen ice-cubes, this will quicken the freezing process. This is because of the heat transferring to the ice under it as well as the evaporation. That's a lot of energy expelling very quickly. But really, you are just shooting yourself in the foot. I mean, if you are trying to get "quick ice-cubes", all you are doing is losing water and making your freezer work harder. So you are spending more money, to get smaller ice-cubes!
Oh no... I'm hearing a smart ass somewhere in the background ... "But what about Mpemba effect!?" The sound of the comic book store Simpson's characters raps upon my ear drums. "Sigh ..." Now are you seriously going to comeback with the grade school kid and his ice-cream milk crap?? Seriously?!?! ARGH!!! okay... fine!!! I admit that the question still remains largely unexplained. HOWEVER, there are some things we can conclude. Yes, evaporation will only account for a small percentile of energy loss (or heat loss in our case). But keeping with what is stated above, we know that we are losing some water to evaporation. Where? Well heat rises last I checked, so that means we are losing from the top. Also, our second point informs us that the heat is transferring to the coldest points. Thus, we are also losing heat from the sides, the bottom as well as the top. "So what! Hot water can still flash freeze and the question still remains unanswered" [Oh that voice is really getting to me!] OK Genius! Yes I do concede the question is still unanswered, but we know that our heat is leaving from the outer portions of the would-be cube. That means the water will freeze from the center first and then out. Cold water on the other hand will freeze from the outside in. Thus insulating the middle from the outer cold.
Now I should technically get into the flash freezing .. but I won't.. WHY?? Because, my earlier point still remains!! You are still spending more energy then is necessary to cool hot water to make ice-cubes, smaller ones might I add! So unless you are a theoretical physicist or any other physicist for that matter - Who the FUCK cares!!! Quit bugging me with this question, as from now on, I'm just going to tell you "Go read my blog!"
Cheers :)
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