People who live in the Great Frozen North often notice in winter time that when cars run in the cold weather, white smoke comes out of the tail pipe, which goes away with the season. It also sometimes goes away if you run the car for a while.

Part One: Why does the white smoke go away?

Part Two: At a generating plant not far from here, on a cold day you can also see the same billowing white clouds of smoke. However, they can also be seen on some warm days, and some cold days, no white clouds. Why is this?

Here's the answer:

When you start your car up, one of the products of this is water in the form of vapor, because of high combustion heat. However, by the time the vapor hits the exhaust system, often times, it has begun to condense, and it is visible. However, on very, very cold days the exaust systm may never get hot enough to keep this from happening. The chimney/smokestack which sometimes had this white stuff coming out burns two different fuels: oil, which is a hydrocarbon or coal, which is a carbon - no hydro.

[ Car Talk Puzzler ]