Combustion question.

[RapidSnail]

My dad had a bet with the guys he works with over the combustion of gasoline. They said that when gasoline burns, it is only the vapor that burns not the liquid and that the liquid can never burn under any circumstances. He says that under certain circumstances (which he has no knowledge of) the heat can be so great that the liquid will burn.

I told my dad that the combustion of liquid fuels can only occur when the vapor oxidizes above its flash point and forms an ignitable mixture (I think). He responded by saying that there must be some point in which the heat is so great (such as the surface of the sun) that the liquid itself is burned. I told him that even though it might appear to have burned the liquid, it still evaporated, oxidized, and burned the vapor, just within billionths of a second. He then asked me whether the liquid itself would burn if it were in a vacuum. I told him that in order to burn, the vapor must be oxidized first, and that there is no oxygen within a vacuum. However, he's still being very adamant about it, insisting that he must be right (because he doesn't want to pay up ). I tried searching for an answer to this question but came up dry. Can any of you absolutely confirm this question either way? He's the kind of person that won't let up unless he has overwhelming proof.

 

[MrBond]

Wikipedia agrees with you (liquid doesn't burn, its vapor does), but that probably won't be sufficent proof for your Dad.

http://en.wikipedia.org/wiki/Combustion

 

[RapidSnail]

I know. The problem is that he's asked several other friends who've agreed with him and that only complicates the matter. Any other confirmations?

 

[acemcmac]

I wish any of my closest relations were smart enough to have that kind of conversation. My girlfriend couldn't figure out the equasion for pi.

 

[imported_Trippin315]

drop a match into a can of gas and see if it lights up.

 

[ElMonoDelMar]

Originally posted by: Trippin315
drop a match into a can of gas and see if it lights up.

He could just argue that only the fumes are burning off in the can.

 

[RapidSnail]

Originally posted by: ElMonoDelMar

Originally posted by: Trippin315
drop a match into a can of gas and see if it lights up.

He could just argue that only the fumes are burning off in the can.

Correct. The flash point for gasoline is -45° C or -49° F.

 

[FoBoT]

so how do solids burn? does a solid have to vaporize before it burns?

or is this some special thing for liquids?


does paper or wood burn? or just paper vapor or wood vapor?

 

[RapidSnail]

Originally posted by: FoBoT
so how do solids burn? does a solid have to vaporize before it burns?

or is this some special thing for liquids?


does paper or wood burn? or just paper vapor or wood vapor?

The solid fuel must be heated until it reaches its firepoint. At that point it begins to give off flammable gases. The gases oxidize and then ignite.

EDIT - I just noticed that you weren't referring to solid fuels but solids.

 

[g8wayrebel]

It is true , only vapors burn. Even wood has to be turned to a liquid to burn the fossil remnants in vapor form. That is why the charcoal forms in a ridged look on burnt wood and it burns in layers. It is also how it is possible to determine the elements and location of a fire starting.

 

[Eli]

Only vapor burns.

If you look closely at paper or wood burning, you can see the separation between the solid and the flame.

 

[Ika]

does this work the same way for non-fuels?

 

[Eli]

Originally posted by: guoziming
does this work the same way for non-fuels?

?

 

[Evadman]

It depends on what you concider 'burning'. If you concider burning the oxidation of another substance, then loquids and solids can both 'burn'. Remember, Rust is the oxidation of iron. If you concider 'burning' in the literal fire sence, then only vapors burn.

 

[her209]

Originally posted by: acemcmac
I wish any of my closest relations were smart enough to have that kind of conversation. My girlfriend couldn't figure out the equasion for pi.

LOL :laugh:

 

[Evadman]

Originally posted by: acemcmac
I wish any of my closest relations were smart enough to have that kind of conversation. My girlfriend couldn't figure out the equasion for pi.

pi is exactly 3.

 

[TheChort]

Originally posted by: guoziming
does this work the same way for non-fuels?

technically anything that burns is a fuel
trying retyping your question more clearly

 

[TheChort]

Originally posted by: Evadman

Originally posted by: acemcmac
I wish any of my closest relations were smart enough to have that kind of conversation. My girlfriend couldn't figure out the equasion for pi.

pi is exactly 3.

isn't that from simpsons when the scientist is trying to get the attention of the other scientists in the room?

 

[ta8689]

Originally posted by: TheChort

Originally posted by: Evadman

Originally posted by: acemcmac
I wish any of my closest relations were smart enough to have that kind of conversation. My girlfriend couldn't figure out the equasion for pi.

pi is exactly 3.

isn't that from simpsons when the scientist is trying to get the attention of the other scientists in the room?

lol something along those lines

 

[RapidSnail]

Originally posted by: guoziming
does this work the same way for non-fuels?

Well I believe that technically anything that is able to be burned is a fuel, so what you're saying is impossible. Correct me if I'm wrong.

 

[her209]

link

What are flammable and combustible liquids?

Flammable and combustible liquids are liquids that can burn. They are classified, or grouped as either flammable or combustible, by their flashpoints. Generally speaking, flammable liquids will ignite (catch on fire) and burn easily usually at normal working temperatures. Combustible liquids have the ability to burn at temperatures that are usually above working temperatures.

There are several specific technical criteria and test methods for identifying flammable and combustible liquids. Under the Workplace Hazardous Materials Information System (WHMIS), flammable liquids have a flashpoint below 37.8°C (100°F). Combustible liquids have a flashpoint at or above 37.8°C (100°F) and below 93.3°C (200°F).

Flammable and combustible liquids are present in almost every workplace. Fuels and many common products like solvents, thinners, cleaners, adhesives, paints, waxes and polishes may be flammable or combustible liquids. Everyone who works with these liquids must be aware of their hazards and how to work safely with them.

Does the liquid itself burn?

Flammable and combustible liquids themselves do not burn. It is the mixture of their vapours and air that burns. Gasoline, with a flashpoint of -40°C (-40°F), is a flammable liquid. Even at temperatures as low as -40°C (-40°F), it gives off enough vapour to form a burnable mixture in air. Phenol is a combustible liquid. It has a flashpoint of 79°C (175°F), so it must be heated above that temperature before it can be ignited in air.

 

[RapidSnail]

Originally posted by: her209
link

What are flammable and combustible liquids?

Flammable and combustible liquids are liquids that can burn. They are classified, or grouped as either flammable or combustible, by their flashpoints. Generally speaking, flammable liquids will ignite (catch on fire) and burn easily usually at normal working temperatures. Combustible liquids have the ability to burn at temperatures that are usually above working temperatures.

There are several specific technical criteria and test methods for identifying flammable and combustible liquids. Under the Workplace Hazardous Materials Information System (WHMIS), flammable liquids have a flashpoint below 37.8°C (100°F). Combustible liquids have a flashpoint at or above 37.8°C (100°F) and below 93.3°C (200°F).

Flammable and combustible liquids are present in almost every workplace. Fuels and many common products like solvents, thinners, cleaners, adhesives, paints, waxes and polishes may be flammable or combustible liquids. Everyone who works with these liquids must be aware of their hazards and how to work safely with them.

Does the liquid itself burn?

Flammable and combustible liquids themselves do not burn. It is the mixture of their vapours and air that burns. Gasoline, with a flashpoint of -40°C (-40°F), is a flammable liquid. Even at temperatures as low as -40°C (-40°F), it gives off enough vapour to form a burnable mixture in air. Phenol is a combustible liquid. It has a flashpoint of 79°C (175°F), so it must be heated above that temperature before it can be ignited in air.

Thanks for clearing that up.

 

[SlitheryDee]

Originally posted by: FoBoT
so how do solids burn? does a solid have to vaporize before it burns?

or is this some special thing for liquids?


does paper or wood burn? or just paper vapor or wood vapor?

I don't know if it's the mechanism by which a solid is allowed to burn, but I do know that the transition from a solid to a gas can occur without the intermediate liquid state. I suppose the resultant vapors could burn.

Anyway it's called sublimation