Why is water used as a car engine coolant instead of alcohol?

[jacklwk]

why we use water, but not alcohol as a coolant in the car engine?can you give me three reasons?

 

[cowmoo32]

Alcohol has a lower heat capcity than water
It boils at a lower temperature than water
It evaporates at a lower temperatuer than water


Why would we use alcohol as a coolant?

 

[jacklwk]

Thx A Lot~

 

[cowmoo32]

Np. All 3 reasons are related. Because it has a higher heat capacity, it takes more engergy to boil, which also means more engergy to evaporate. Was this a homework question, or were you just wondering?

 

[jacklwk]

actually this is a homework question.
i am just a secondary 3 student.
can i say water is cheaper and alcohol is flamable?

 

[cowmoo32]

I'm not sure those would be better reasons than the ones I listed above. The fact that alcohol is flammable shouldn't be a factor because it is never exposed to a spark, only the gasoline is. If the water was ever present where the combustion took place, the engine wouldn't run. Also, inside the radior, some of the water does boil; that's why you don't open a radior cap on a hot engine. Not all of the water boils because it's under pressure. If alcohol were used, more of it would boil and you wouldn't have the same volume of cooling liquid inside the radior; more would exist in a vaporous form than with water.

 

[jacklwk]

THX for your detailed explanation!You are really a enthusiast!

 

[cowmoo32]

Haha. I do love cars, and the test I'm studying for right now deals with heat capacity. Good thing you asked when you did.