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My five year old is just question after question and has just stumped me. He wants to know why when a tyre burns, the smoke is black, but when a car spins it's tyres, the smoke is white? Anyone got an answer for him :-?

Matt

Good morning Matt...

The only answer I can think of right now is:

"Go ask your mother"...

You have to love it when they are at that age.

You are not actually "Burning" the tire (ie - setting on fire). You're melting off the tire which is why you're left with nasty black marks on the street. The smoke is a result of the rapid oxidation of certain compounds in the tire. The chemical combination includes both hydrogen and carbon. This gives us carbon dioxide and water vapor resulting in a white smoke.
When people do burnouts for so long that it actually ignites the tires then you get carbon in the mix, producing black smoke.

At least that is what I think.

The black smoke is caused by a chemical reaction from the rubber burning.

The white smoke is caused by friction, and lacks the toxic chemicals that make the smoke black.


That's just my guess, but it sounds good. 

[quote]The black smoke is caused by a chemical reaction from the rubber burning.

The white smoke is caused by friction, and lacks the toxic chemicals that make the smoke black.


That's just my guess, but it sounds good.

Maybe the chemical composition of the tread area is different from the rubber of the "core" of the tire?  Don't know.

Your child has asked a good question!  Hummmm.............

best,

...................john

Question from a 67 year-old. Is the white smoke actually smoke or steam?

Question from a 67 year-old. Is the white smoke actually smoke or steam?

Smoke. Steam don't stink like that!

[color=#000000]My memory fails me here, but years ago, I learned that the black marks on pavement are not all from the spinning tire. Some of it is from the pavement itself, caused by the friction and though it was not mentioned, I think may also have to do with the smoke. And some tires, including the Dunlops on my Camaro, do not even leave a mark. I think it has to do with the particular compound, in this case, very soft. They do put up a lot of smoke though.

Having said all that, here is what I believe to be the correct answer from Poplular Mechanics.
[quote] When tires smoke from spinning on the pavement, they

Hi Guys, thanks for the collective answers. Patchz, the PopMech link was great, I am a PopSci subscriber, maybe I should change until he can work it out for himself. For a five year old he amazes me. My workshop and tool kit is now firmly under lock and key

Matt

My workshop and tool kit is now firmly under lock and key

Matt

[color=#000000]Based on experience, I would say that is a wise move.

The exact answer from the link: Q: When old tires are burned they emit thick, black smoke. But when NASCAR cars slide sideways or do victory burn-outs, the smoke is pure white. Why the difference?

A: When tires smoke from spinning on the pavement, they

Hi Guys, thanks for the collective answers. Patchz, the PopMech link was great, I am a PopSci subscriber, maybe I should change until he can work it out for himself. For a five year old he amazes me. My workshop and tool kit is now firmly under lock and key

Matt

I would get him his own subscription.
His age, getting male with his name on it, he will love it.
And he will love looking at it, and may improve his reading faster, esp when you read it with him.