FtG (12/15/82)
I've always enjoyed puzzling over the mysteries of everyday phenomenon and I am usually successful in figuring out what is going on, but I recently noticed something that has me stumped. Perhaps someone out there in netland can solve this one. When boiling water is poured over teabags, the bag very quickly fills up with air. I found this annoying since I think it interferes with the brewing. I can suggest four causes, but I am not satisfied with any of them. There are listed below in the order of almost plausible to the far fetched. 1. Thermal expansion of latent air in the bag. It appears that the amount of air at least triples, but the coefficient of expansion of air is less than .004/Degree C., which can only account for an expansion by about 1/3. 2. Formation of water vapour, the tea leaves being great nucleating sites. There are several problems with this- a) Not that much vapor should form at the temperatures one expects in the cup shortly after pouring (the water cools down very quickly), b) The vapour should recondense quickly when the bag bobs to the surface. 3. Agitation- the act of pouring the water in stirs up the bag quite a bit, but how this causes so much air to be "pumped in" is beyond me. 4. Volatile oils in the tea. The herbal teas I drink contain lots of volatile oils which might form a nice vapour inside the bag when heated, but I don't think it could possibly account for all of the swelling. Comparing regular teas to herbal teas may be useful. 5. Its God's will. (Included to give Creationists equal time :-) ) Mail your ideas and arguments to me and I'll post back to the net the best solutions if interest warrants. Does anybody else out there have a favorite phenomenon they can't explain? rocheste!FtG
York@MIT-MULTICS (12/17/82)
From: York at MIT-MULTICS (William M. York) Here is a related question for you: After you take your teabag out, you hear the phone ring. You know you may be gone for a while and you want your tea to remain as hot as possible. You always add N ounces of cold milk to your tea before drinking it. In order to maximize the temperature of the tea in T minutes from now should you add the milk now or wait until you come back and are about to drink the tea?
debray (12/24/82)
With regard to the question of when to add cold milk to hot tea so as to have the tea as hot as possible after the phone has been answered : Obviously, one should add the milk BEFORE going to answer the phone, since heat loss is proportional to the difference in temperature between the cup of tea and the surroundings. I mean the Rate of heat loss. Saumya Debray