[kenny1999]

what is the scientific definition of the term " flammable " ?

is it true to say that the lower b.p. is an organic compound (or the more volatile is it)

then the more flammable it is?


by the way, what is the difference between "flammable" and "inflammable"?

[discodermolide]

what is the scientific definition of the term " flammable " ?

is it true to say that the lower b.p. is an organic compound (or the more volatile is it)

then the more flammable it is?

No this is not correct, think of fluorocarbons which have very low BPts they are not flammable.
Perhaps you should look at the MSDS of several organics and compare the flame point and the flash point.

[Honclbrif]

Flammable really just means that under the correct conditions the material can be ignited. "Inflammable", to the consternation of many, means "easily ignitable" (Ugh, what a country!)

In regard to the second part of your question, volatility and flammability are not the same. Chloroform, for instance, is rather volatile, but inflammable.
http://www.osha.gov/SLTC/healthguidelines/chloroform/recognition.html

You seem to be thinking of flash point, which can confuse people. Flash point does not refer to the ignition temperature of a substance, but instead refers to the minimum temperature a liquid must attain before the vapor density is sufficient to be ignited by an open flame. This is related to volatility, as more volatile substances will have higher vapor densities at lower temps, but is also related to the reactivity of the molecule in question as well.

[Honclbrif]

As a second example to compliment chloroform I would bring up paraffin, which is very flammable, but not very volatile.

[kenny1999]

You seem to be thinking of flash point, which can confuse people. Flash point does not refer to the ignition temperature of a substance, but instead refers to the minimum temperature a liquid must attain before the vapor density is sufficient to be ignited by an open flame. This is related to volatility, as more volatile substances will have higher vapor densities at lower temps, but is also related to the reactivity of the molecule in question as well.

excuse me... sir... I don't understand what you are saying?

what is flash point?? can you explain it a little bit more detailed? Sorry

[Honclbrif]

Usually when a liquid burns its not actually the liquid that's burning, but the vapors, and in order to burn they need oxygen. Too little oxygen and the mixture is too "lean" to burn. The flash point of the liquid is the temperature the liquid has to be warmed to for the vapor pressure over the liquid to be high enough that those vapors can be ignited by an open flame. The vapor pressure in the air over the liquid is related to the temperature of the liquid.

Take for instance, diethyl ether: boiling point = 36.4°C; flash point = -45°C

At -45°C, the ether is warm enough to have produced enough vapors to be ignited.

On the other hand, toluene: BP = 110.6°C, flash point = 4°C

Toluene must be warmed to 4 degrees until the vapor pressure is high enough for them to be ignited.

[Dan]

Flammable really just means that under the correct conditions the material can be ignited. "Inflammable", to the consternation of many, means "easily ignitable" (Ugh, what a country!)

In regard to the second part of your question, volatility and flammability are not the same. Chloroform, for instance, is rather volatile, but inflammable.
http://www.osha.gov/SLTC/healthguidelines/chloroform/recognition.html

Just to flag up a possible source of confusion - Inflammable does mean easily ignited, but chloroform is non-flammable (the opposite of inflammable). Dichloromethane would be another example of a highly volatile compound with a very low flammability.

[Honclbrif]

Whoops! Thanks for catching that careless statement on my part, Dan. I need to be more careful with my terminology.

[BobfromNC]

The term "flammable" is frequently used to describe any material with a flash point at or below 100 degrees C, such as gasoline or diethyl ether.  If the flash point is above 100 and below 200 degrees C, such as Diesel fuel, those chemicals are referred to as combustible, meaning they will burn, but are much harder to ignite.   So diesel will not readily ignite if below 100 degrees C, but gasoline will ignite from a spark at any temperature above -40C (its flash point).  That is the DOT (dept. of transportation) definition, used to classify liquids for shipping purposes.

(Actual flash point test is based on if a specific sized spark/hot wire will ignite the material at that temperature, I believe.)

Bob