Open Systems

[tinman]

Wrong.  The product of the number of molecules and their temperature determines the energy which is equal to the pressure * volume product scaled by Boltzmann's constant.    Now your energy which is proportional to n*T has fallen.  That last bit is a tangled mess.

What you keep missing is that any external work performed by expanding the gas reduces the PV product.

What you keep missing is that the PV product has nothing to do with the mass amount.

IE the gas temperature falls.

The over all gas temperature remains the same,and has nothing to do with the temperature of the gas coming from the gas injector nozzle insid ethe heater.

It's gone, over, done

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The mass remains,and thus so dose the energy contained within that mass of gas.

[profitis]

Mark E and libre will continue to ignore the most important aspect of the system @tinman.the phase change liquid>gas.the gain is here and here alone

[MarkE]

What you keep missing is that the PV product has nothing to do with the mass amount.
The over all gas temperature remains the same,and has nothing to do with the temperature of the gas coming from the gas injector nozzle insid ethe heater.
.
The mass remains,and thus so dose the energy contained within that mass of gas.

Well first dear tinman I have not talked about mass in this discussion.  Why you bring it up is a secret of your own.  The PV product is a measure of the gas PE, which is also measured by nRT, none of which are mass specific until we talk about particular types of molecules.

What you keep missing is basic thermodynamics that has been established for almost 200 years.  If you are just going to proverbially jam your fingers in your ears and shout "na, na, na" there is no discussion.

[MileHigh]

I get the impression that Tinman is not recognising that there are two separate and distinct energy components related to the discussion:

1.  The chemical energy associated with the H2 and O2 gas resulting from the splitting of the water.  Nobody is disputing this.

2.  The energy dynamics related to the compression and expansion of the gas itself.   It's like the gas is a kind of compressed spring that can store and release energy.  In this case it doesn't matter what the chemical composition of the gas is.  The discussion about the laws of thermodynamics is all about this aspect.

[MileHigh]

Mark E and libre will continue to ignore the most important aspect of the system @tinman.the phase change liquid>gas.the gain is here and here alone

Go back and look at my simplistic analogy using the ping pong balls metaphor.  Where does the energy come from to evaporate a liquid?  How is there a "ping pong bat" in the liquid to launch a ping pong ball out of the park?

That energy comes from the heat stored in the liquid itself or in the ambient environment around the liquid.  The nature of the molecular motion is that the molecules have a kind of normal distribution for their velocities.   Sometimes there is a high velocity collision in the right direction to launch a ping pong ball out of the park.

There is no energy gain at all.   The high velocity ping pong ball that has escaped the liquid is balanced out by the fact that the liquid has lost some thermal energy.