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[Beezabryan]

Further to my earlier post I spent a while in my garage, first I drained the crankcase of lube that had accumulated in the crankcase over the past 5 months.
Went through the normal starting procedure, took three swings to wake up the lazy bugger.
left it running until most bits were warm.
Now I have to wait until both me and the weather are fitter before digging out the riding gear for an outing.
NB the small amount of fuel left in the tank was bought in June last year.
All achieved without a single scientific cogitative episode

[PeteF]

OK, my last word on the subject.
The following is from a friend of mine. Tom has a Doctorate in chemistry.
Hi P. This takes me back! Reaction between hydrogen & oxygen is spontaneous; ie, energy of reactants is higher than that of product. BUT reaction only occurs between atomic H & O. So, unless molecular H & O are first converted to separate atoms it is my considered opinion that they won't react. Can do this by providing activation energy (heat). However, a catalyst could be used (platinum) but I still think some heat would be needed. If molecular H & O did react there wouldn't be much left in the atmosphere by now. Hope this helps. All best, T.

[Dennis C]

Is it safe to come out yet?.

[Beezabryan]

Probably not yet Dennis

[Dennis C]

O heck, ducks and runs.

[jefrs]

Thack - not everything in wiki is correct, hydrogen does not have to burst into flames (it does if you want to power a rocket).

PeteF, Tom is correct in that it needs activation energy (I mentioned that) but he also uses the word 'spontaneous', ask him to release some small amount of hydrogen into a gas jar full of ordinary air, wait an appropriate period and then measure how much H is left, mention probability of reaction and reducing atmospheres. Yes, they do react more easily plated onto a surface (could be dust) or dissolved in water (think rain droplets), real world stuff.

There is little to none free hydrogen in the atmosphere, so where has it gone? Why do we still have free oxygen, because hydrogen bonds more strongly to carbon etc.

This stuff applies, where does that energy come from? - http://chemwiki.ucdavis.edu/Physical_Ch ... n_Energies

kJ/mol is a big number but the mol is an Avogadro's number of molecules, 6.0221409e+23, a googleplex, so the energy required for a pair of molecules to kick off from kinetic collision or thermal energy (vibration) is miniscule.

Applying heat increases it's temperature right, temperature is a vibrational energy (we use Kelvin), so the hotter it is, the more energy it has in itself.



Yes, petrol will burn without compression but any fuel/air burns more easily and more quickly and completely if compressed pushing the molecules and hence the flame path together. So quickly that the piston will hardly have moved by the time it is finished, it is the expanding hot product gases and now very hot nitrogen (the other stuff in air) that drives the piston down the cylinder rather than the force of explosion as such (we don't really want that too strong, it blows a hole in the piston). The idea of using higher compression is to get better combustion and hence increased power output, better thermodynamics if you like.

[PeteF]

I give up.

[Thack]

PeteF writes: "I give up."



Me too! Our mate jefrs is obviously having a bad couple of days. We should let him have the last word, as it seems so important to him.

[Beezabryan]

Amen

[Dennis C]

I gave up with him weeks ago, the guy is perfect and never gets anything wrong, oops sorry that should read never owns up to his many mistakes.