Our organic teacher stated today that commercial gasoline ranges from .71-.79 g/cm^3 today in lecture. Why does gasoline have various values of density?

 

Does it have anything to do with the various octane ratings you can purchase? Are there any other reasons?

It's actually got to do with temperature. Fuels at different temperature have different densities.

The density of gasoline (C8H18) is 0.694 g / cm^3 at 300 K and 0.622 g / cm^3 at 400 K.

Hoped I helped. :3

Not just fuels most things.

Gasoline is not made of uniform molecules, like f.e. water.

 

Even water is not quite uniform.

It can be made of H₂O, D₂O or HDO,

Oxygen can be Oxygen-16, Oxygen-17 or Oxygen-18 isotopes (these are stable).

Hydrogen can be Hydrogen-1, Deuterium or Tritium (it has 12.32 years half-life).

 

Heavy water (D₂O) won't have the same density (1.11 g/cm^3) as pure water H₂O (1 g/cm^3).

 

With gasoline it's much more complicated.

 

Octane C₈H₁₈ is one of gasoline components.

Different gasolines can have different amount of octanes

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

Edited October 2, 201411 yr by Sensei

It's essentially the proportion of carbon (denser) to hydrogen (lighter) that determines the density. Bigger alkanes are denser, and aromatics are denser than alkanes. Then, minor differences exist among the isomers.

 

No direct relationship with the octane rating (which takes iso-octane as a reference), except that aromatics, when present, bring both a high octane rating and a high density. But cetane and Diesel oil are denser than iso-octane and have a very low octane rating.