fossil fuel?

pivoxa15

Fossil fuel is former live organic matter which has bee buried for hundreds of millions of years. They have lots of energy in them and we use it by burning them and converting some of those energy into useful work.

What energy is that?
Why does fossil fuel have so much more energy compared to living or recently dead organic matter?
What percentage of the energy of fossil fuel was already in them just before they died and what percentage did they gain after millions of years underground?

Bystander

Looks like homework. Smells like homework. Must be homework.

Give the first two questions a try; the third is poorly stated, and you'll want a little help with the restatement --- once you've got the other two.

pivoxa15

Actually it is not homework. It is something that came up during a discussion in the General phsyics forum under the topic of Hot Food.... But I'll have a go at answering the first two questions.

1. All the energy we derive from fossil fuel by burning it was in the form of chemical energy.

2. Because it has been underground for hundreds of millions of years and static most of the time, it has accumulated massive amount of gravitational and thermal energy and has converted it into 'extra' chemical energy (on top of the chemical energy it had while it was alive through photosynthesis). It is this 'extra' chemical energy accumulated through millions of years that makes fossil fuel so energy rich.

3. The answer to this questions depends on the (correct) answers to 1 and 2. So I can't answer it. It may need to be restated as well.

Bystander

Sorry --- haven't been following that thread.

Correct --- underline, bold-face, and emphasize in every possible way the word "All."Creative. Absolutely, utterly, totally wrong, but creative. Give ya a couple hints here, and let you try again:

1) how much nutritional value in a glass of water? (You've already covered that in the other thread, but think about it.)
2) Ever use dehydrated soup? What's the label on the package say about nutrition? How does it compare to that for a "serving" of the same canned soup? How much nutritional value do you add to dehydrated by rehydrating it?

Gotta wait on 3. until we finish 2.

'Nother point for you, just to correct some miscalculations in the other thread --- a dietician's calorie (or "great calorie") is 1000 times larger than a thermodynamic calorie --- the thermal energy from heating food is 1000 times less relative to nutritional energy than everyone has been calculating in the "hot food" thread.