This is getting ridiculous! Water is probably the most-studied chemical
compound, and still the least understood. With good reason - it has
several properties that do not correspond with expected trends. Anyway,
here are some FACTS --- write them down, please:
Water has a specific heat of 1.00 calorie per gram per degree C. i.e. it
takes 1 calorie of heat to raise the temperature of 1 gram of water 1
degree (at 20degC). The specific heat of water is *defined* as 1.00; the
value for all other substances is relative to water.
The specific heat of ethylene glycol is 0.56 cal/g/degC. What does this
mean? Ethylene glycol does not absorb heat *nearly* as effectively as
water! One gram of ethylene glycol only absorbs 56% as much heat as one
gram of water.
The fact that mixtures of water and ethylene glycol raise the boiling point
of the mixture is not related to its ability to absorb heat. (Well, not
*very* related.) The anti-boil and anti-freeze phenomena are known as
boiling-point elevation and freezing-point depression and are general for
*all* mixtures.
As someone else has pointed out, elevation of the boiling point should not
be of much concern anyway. We normally want our cooling systems to operate
20 to 30 degrees (F) below the boiling point of water. The fact that we
are using a pressurized system means that the boiling point is actually
above 212 F, also. A pressure of 15 pounds might raise the boiling point
by 15 to 20 degrees F.
A "water wetter" is useful because of the rather large amount of surface
tension generated by pure water. There are lots of things that make good
wetting agents, including plain old soap, but you don't want that in your
radiator. ;-) A wetting agent both promotes better contact between the
metal surfaces and the water, and helps bubbles either dissolve or just
break up into smaller bubbles. Last Saturday I took my 5-year-old to a
"chemistry" show where this was demonstrated.
I don't want to get back into the fracas about the usefulness of
antifreezes, but in our daily drivers they are helpful in keeping the
water chemistry calmed down, due to the presence of additives that
stabilize the mixture and buffer the pH of the system.
Lee M. Daniels - Laboratory for Molecular Structure and Bonding - Texas A&M
daniels@lmsbvx.tamu.edu | DANIELS@TAMLMSB.BITNET | (409) 845-3726
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