jj@alice.UUCP (05/10/85)
OK, we've been through the "hot water/cold water freezes faster" routine, we've been through the "water heater mineral" routine (several times, in fact), and we're going through the "cold water boils faster" routine right now. In case anyone cares, I have tried all three experiements: In the first, cold water easily outfroze hot water when both were put in identical trays in opposite ends of a freezer with nothing else inside it. (they were both arrayed front to back, and the opening/closing of the freezer was clearly not likely to affect either one more than the other.) The freezer has no blower, and the coils are in the bottom, thus they affect each tray equally. A letter in Scientific American covered this subject a few years ago, noting that that it necessarily took more heat to freeze hot water, but that hot water made some refrigerators turn on sooner, thus speeding the freezing process. Putting both in the freezer at the same time negates the effect of the refrigerator duty cycle. In the second, I WEIGHED my old water heater when I got rid of it (It was dead, and I had put in a new one in a different location...) and it weighed several pounds more than its original shipping weight, which requires it to be heavier when removed than when installed. That more or less proves that over its lifetime, it had minerals precipitated OUT into it, thus leaving less total minearl content in the hot water. In the third, practiced after lunch with a microwave oven, hot water boiled much faster than cold water. Each was put into the oven alone, and the time to boiling was measured. Equal amounts of water were used for both hot and cold water, and the same container was used. Both times, the container was put in the middle of the oven. The cold water was, in fact, put into a slightly warm container, thus giving it a slight advantange, so if any bias existed, the cold water was favored. So much for these three old (and well known) folk tales. Can we talk about how to make good Samosa and Dhosa's now. Pleeeeze? I suppose that net.physics could be a home to these discussions, they certainly don't relate to cooking, except in that the cold water you use for tea and coffee has more disolved air, and tastes better as a result. -- TEDDY BEARS ARE OPINIONATED! AFTER ALL, SOMEONE HAS TO BE RIGHT! "Then one said to the other, I think we must be gone, We'll leave a present for our friend before me move along..." (ihnp4/allegra)!alice!jj
roy@gitpyr.UUCP (Roy J. Mongiovi) (05/16/85)
> Scientific American covered this subject a few years ago, > noting that that it necessarily took more heat to > freeze hot water, but that hot water made some refrigerators > turn on sooner, thus speeding the freezing process. That sounds quite reasonable to me. > In the second, I WEIGHED my old water heater when I got rid of it > and it weighed several pounds more than its original shipping weight... > That more or less proves that over its lifetime, it had minerals > precipitated > OUT into it, thus leaving less total minearl content > in the hot water. Actually, all that proves is that more minerals entered the tank than left it. It says nothing about the mineral content of cold water. I know that in my apartment complex the hot water has considerably more rust than the cold. If I make macaroni starting with hot water I get orange macaroni.... > In the third, practiced after lunch with a microwave oven, > hot water boiled much faster than cold water. Well, I think this really depends on your definition of boiling. Remember chemistry lab, when you put boiling chips in the liquid to speed up boiling and to prevent the solution from exploding? I think the dissolved oxygen in cold water has an effect like that. As you raise the temperature of water it can dissolve less oxygen, and the O2 starts to bubble out, thus aiding the start of boiling. I don't think there is any question that it takes longer to get cold water to 100c than hot water, but it might take less time for cold water to start to bubble. A microwave heats differently, and this may have masked that result. -- Roy J. Mongiovi. Office of Computing Services. User Services. Georgia Institute of Technology. Atlanta GA 30332. (404) 894-6163 ...!{akgua, allegra, amd, hplabs, ihnp4, masscomp, ut-ngp}!gatech!gitpyr!roy