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Jet fuel is a mixture of hydrocarbons. Almost all the chemical bonds that the carbon atoms (with a relative weight of 12) are linked in are either to another carbon atom or to a hydrogen atom, the latter having a relative weight of 1. Thus, jet fuel is almost all carbon, with the residue almost all hydrogen.

When you burn it, you break those carbon-carbon and hydrogen-carbon bonds and combines each atom of carbon with two atoms of oxygen, which together have a relative weight of 32. Now you've gone from a relative weight of 14 (-CH₂-) to a relative weight of 44 (CO₂) (yeah, I know there are CH₃ in there and other combinations, but this is a ball park estimate). Multiply the weight of the jet fuel times the fraction of it that is carbon (say, at least 90%, so use 0.9). Then multiply that in turn times 44/12 (~ 2.44). That gives you the mass of CO₂ that is generated from burning a given mass of carbon.

Theoretically, you could actually freeze that into dry ice and weigh it. You get the great increase in mass because the weight of the oxygen attached to the carbon is more than 10 times the weight of the hydrogen whose place it's taking.

Theoretically, you could actually freeze that into dry ice and weigh it.

Makes much more sense now, especially since I'm talking "theoretical" anyway.

I think I can work with and understand your computations now. Thanks.

“You get the great increase in mass because the weight of the oxygen attached to the carbon is more than 10 times the weight of the hydrogen whose place it’s taking.”

Increase in ‘mass’ or density???

Where does the oxygen come from?

What happens to the C02 that goes into our atmosphere? Does it stay C02?