Why are some fuel sources better than other fuel sources?

[nec209]

Why are some fuel sources better than other fuel sources? I mean some things are better fuel sources than other fuel sources.Some things burn easy and other things do not.

Some fuel sources have more energy than other fuel sources.Where has other fuel sources have less energy

example it hard to get car to run on water ,oxygen or helium and yet other fuel sources like wood or fossil fuels very easy and have lots more energy.

[swansont]

Are you just going by what burns as being "better"? Then it's the bonds that are present, and how much energy is released if bonds are replaced by bonding with oxygen. It's also a matter of what the activation potential is — the oxygen needs to be energetic to get close enough to bond to the material and replace the other bond, which dictates how hot the material needs to be to ignite.

 

Water already has bonds with oxygen, so water isn't going to burn. Helium doesn't bond, period. Oxygen usually comes in diatomic form, so it needs to bond to something else. Wood and fossil fuels, on the other hand, have lots of hydrogen and/or carbon, both of which readily bond with oxygen. There is a net release of energy when that happens, and given enough of the materials involved, they don't have to get particularly hot for this to sustain itself.

[nec209]

Are you just going by what burns as being "better"? Then it's the bonds that are present, and how much energy is released if bonds are replaced by bonding with oxygen. It's also a matter of what the activation potential is — the oxygen needs to be energetic to get close enough to bond to the material and replace the other bond, which dictates how hot the material needs to be to ignite.

 

Water already has bonds with oxygen, so water isn't going to burn. Helium doesn't bond, period. Oxygen usually comes in diatomic form, so it needs to bond to something else. Wood and fossil fuels, on the other hand, have lots of hydrogen and/or carbon, both of which readily bond with oxygen. There is a net release of energy when that happens, and given enough of the materials involved, they don't have to get particularly hot for this to sustain itself.

 

 

I thought more densely packed molecules more energy output and more fual efficient.Where less densely packed molecules less energy output and less fual efficient.

 

I said the problem is fuel they are using and they have to find other fuel source that has more energy thus more fual efficient.

 

example possible to get cars to run on other fuel sources other than fossil fuels that has more energy thus more fual efficient.

[Sensei]

I thought more densely packed molecules more energy output and more fual efficient.Where less densely packed molecules less energy output and less fual efficient.

 

It's true only for special cases like f.e. Hydrogen and Oxygen in gas or liquid state of matter.

Simply result of that the higher density, the more atoms/molecules in the same volume.

 

I thought so you are interested in comparison of completely different substances like f.e. methane, ethane, propane, gasoline, methanol, ethanol, isopropyl.

 

f.e. methanol has more molecules than ethanol per cm^3

but has less energy per kg and per L.

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

Edited April 22, 2014 by Sensei

[EdEarl]

 

 

I thought more densely packed molecules more energy output and more fual efficient.Where less densely packed molecules less energy output and less fual efficient.

 

I said the problem is fuel they are using and they have to find other fuel source that has more energy thus more fual efficient.

 

example possible to get cars to run on other fuel sources other than fossil fuels that has more energy thus more fual efficient.

There are other possibilities, for example Hydrogen. Burning hydrogen makes water, which is nice, but hydrogen is not a very dense fuel; thus, pre gallon you get more distance from diesel or gasoline. On the other hand, diesel and gasoline put CO2 into the atmosphere, which is the reason for considering hydrogen as a fuel, its only byproduct is water.

 

Biofuels, such as biodiesel, alcohol, and wood, put carbon into the atmosphere, but to grow them removes the CO2; thus, they are carbon neutral. They neither add nor remove carbon from the atmosphere for a complete grow, make use cycle. Thus far, oil is less expensive than biofuel.

 

The navy has recently announced a process to remove CO2 from sea water and make jet fuel, which is a carbon neutral process. I don't know anything about the economics.

[swansont]

 

 

I thought more densely packed molecules more energy output and more fual efficient.Where less densely packed molecules less energy output and less fual efficient.

 

I said the problem is fuel they are using and they have to find other fuel source that has more energy thus more fual efficient.

 

example possible to get cars to run on other fuel sources other than fossil fuels that has more energy thus more fual efficient.

 

 

That's a matter of whether you think energy per unit volume is better or energy per unit mass, or some other criterion. You can pressurize a gas or even liquify it, or store hydrogen in metal hydrides to improve the density.

 

When it comes down to it, you're probably looking at trade-offs between multiple factors, not all of which can be optimized.

[nec209]

Simply result of that the higher density, the more atoms in the same volume.

 

 

And the more energy it has? I think what I'm confused is understanding why some fuel sources have more energy than other fuel sources.Why some fuel sources are just not practical. Where does the energy come from.Is it releasing the electrons in the atom or the density?

 

That look at space rocket it takes fuel to launch a mass into space but the fuel itself has mass its a bit of a problem. That's why current rockets are multi-stage clamber to reach orbit. The fuel packs just enough of a punch to make the trip at all. A rocket 90% of it is fuel just to take up 5% to 10% of payload.

 

From what I understand the fuel rockets uses is the most densely packed fuel.

 

Same with cars and airplanes very costly and not fuel efficient.

 

That why I said they need to find other fuel source.But I'm not understanding the chemistry of this.Why some fuel sources are better than other fuel sources.Why some fuel sources are just not practical.Some fuel sources have more energy than other fuel sources.

 

Why the fuel sources they are using now is not fuel efficient.They have to find other fuel source that is more fuel efficient.

[swansont]

That why I said they need to find other fuel source.But I'm not understanding the chemistry of this.Why some fuel sources are better than other fuel sources.Why some fuel sources are just not practical.Some fuel sources have more energy than other fuel sources.

 

Why the fuel sources they are using now is not fuel efficient.They have to find other fuel source that is more fuel efficient.

 

As I said, the energy is from the difference between the bonds you break and the new bonds you make. The problem is that new, really strong bonds are hard to come by, because nature has usually already made those molecules — the reactions occur spontaneously. What you're left with is pretty strong bonds, but with that activation potential I mentioned, so they don't spontaneously form near room temperature — they need an extra "kick".

[nec209]

Any thing I read is Combustion also known as burning is chemical reactions between fuel and an oxidant accompanie combustion reaction, a compound reacts with an oxidizing element, such as oxygen or fluorine and the products are compounds of each element in the fuel with the oxidizing element.

 

I think what I'm not understanding is oxidant and why oxygen or fluorine only thing thing that will allow burning.I think I may be confusing it with rockets has in space there is no oxygen so how does it work.

 

Looking up what is Fuels (Fuels are any materials that store potential energy in forms that can be practicably released and used for work) only show three types chemical energy that could be released through combustion , nuclear energy (via nuclear fission or nuclear fusion or cellular biology process known as cellular respiration.And chemical energy or cellular biology need oxygen for it to work.I gusess I'm confused why it only works with oxygen and confusing it with space rockets.

 

Also I think I may be not fully understanding how internal combustion engine work.I know internal combustion engine is an engine in which the combustion of a fuel occurs with an oxidizer ( air) in a combustion chamber.Again internal combustion engines depend on combustion of a chemical fuel with oxygen from the air.

 

Cars and airplanes are air-breathers reactants need to oxidize in air.So it seems fuels burn easier than other fuels because they combine with oxygen better. So if there was no oxygen tha cars or airplanes would not work , it would have to carry its own oxygen tank for burning of fuel to work. Or other way saying it for internal combustion engine to work need oxygen. I think I'm confuing it with rocket engines and why oxygen is needed.Why burning of fuel does not work with out oxygen.

 

Some fuels burn easier than other fuels because they combine with oxygen better.But why oxygen is needed. Any other ways for fuels burn wit out oxygen.

Edited April 24, 2014 by nec209

[swansont]

Burning is by definition an oxidizing reaction. That's the name we give to it.

 

Rockets carry the oxidizing agent with them. You may have run across the term LOX, which is liquid oxygen. Solid rocket fuels have oxidizers in them.