In a message dated 5/21/02 11:10:14 PM Pacific Daylight Time, [EMAIL PROTECTED] writes:
> From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] > Sent: 21 May 2002 18:42 > To: [EMAIL PROTECTED] > Subject: [PEN-L:26130] Re: Re: gould dies at 60 > > >(Thus water after it is heated up gradually, > >suddenly begins to boil. > > If you're going to show this book to people who are of a pedantic > disposition, you might want to find a different example. This isn't true of > water, which gradually approaches boiling point along its boiling curve. > Boiling is the limit of a process whereby the heat lost from evaporation > increases as a liquid is heated; it's the point on the boiling curve at > which the heat loss from evaporation exceeds the heat applied, if I remember > O-level physics right. > > The freezing of water as it is gradually cooled is much more like the > discontinuous process you want; supercritical liquids can freeze all in an > instant. But liquids come to the boil gradually. > > dd Daniel-- Boiling and freezing, like all physical processes are indeed quite complex when you start to look at them closely. This does not negate the point I was attempting to make. The boiling point of water is usually defined as the temperature at which the maximum (or "saturated") vapor pressure of a liquid is equal to the prevailing atmospheric pressure. (This is why the boiling point varies with altitude.) But water, like all other liquids, does NOT necessarily boil at its boiling point! Water can be super-heated, that is, raised above its boiling point without boiling, just as it can be super-cooled (lowered below its freezing point without freezing). There are a variety of factors which either facilitate this or make it less likely. (Adding a thin film of oil over water is one way to facilitate it.) If anyone really wants to get into some of the further complexities of the boiling process, I have explored this particular example in considerable depth in my essay "Notes on 'Notes on Political Economy'", especially the section entitled "Thresholds and 'Absolute' Thresholds". This essay, by the way is a critique of the recent philosophical methodology employed by the Revolutionary Communist Party, USA, with respect to both political economy and its general political appraisal of the world situation. It is posted at: http://members.aol.com/ScottH9999/essays/NotesNPE.htm It is true that water does not begin to boil at an instaneous moment. Boiling itself is a process, and all processes take time. But compared to the long period of heating that it normally takes to raise water in a tea kettle, say, to the boiling point (or rather to where it "starts" to boil), the boiling is a sudden qualitative change. The way to really understand this is to recognize that overall in virtually any process there are two periods--a period of gradual change, which leads up to a period of sudden transition. But even the period of sudden transition takes SOME time; it is just that the time it takes is very short in comparison with the time typically required by the period of gradual change. The key principle of dialectics here is the interpenetration of opposites. There are actually dialectical leaps within periods of gradual change, and there are actually periods of gradual change within dialectical leaps. Hope this helps. --Scott Harrison
