How is it that coolant, aka "anti-freeze", can protect against both hot and cold temperatures?

Dear Car Talk

Dear Car Talk | Jul 01, 1996

Dear Tom and Ray:

This is not really a car question, but it has to do with a
car. It will help you to know that I'm from Canada, where
winters are very cold. My husband kept running away, then I
met this great guy, married him, and moved with him to
Arizona where it is hot, hot, hot! Now, he has run back to
his ex. I realize you can't help me with my "men" problems,
but maybe you can answer this question for me. Why is it
that in the blistering heat of Arizona and the freezing cold
of Canada, one product -- antifreeze -- can protect against
both? How is this possible? -- Lea

TOM: Great question, Lea. How can one little liquid keep
your car from overheating in the summer AND freezing in the
winter? The answer, in a word, is "contamination."

RAY: Not like what the editors have done to this newspaper
by running our column here. We're talking about actual,
honest-to-goodness chemical contamination.

TOM: We know that water normally freezes at 32 F and boils
at 212 F. But a funny thing happens when you "contaminate"
the water with another substance. The freezing point goes
down and the boiling point goes up!

RAY: And when you mix ethylene glycol (a k a antifreeze)
with water in approximately a 50-50 ratio, the mixture has a
freezing point down around 35 or 40 below zero and a boiling
points upwards of 265 F. Pretty cool, huh?

TOM: So now that we've solved that little mystery for you, I
wonder why men keep running away from you. I can empathize,
Lea, because I have the same problem with little kids.

RAY: Yeah. But THEY run away screaming!

Get the Car Talk Newsletter

Got a question about your car?

Ask Someone Who Owns One