What's wrong with this

[MarkE]

Unless you change the state of that material.
Energy is used to convert the liquid to gas, 75% of which is returned when the gas is converted back to liquid. This leaves the onboard turbines a task of generating the remaining25%

No, a thousand times no.    A mole is a mole is a mole is a mole.  Material state is related to the volume a given mass occupies.  It does not change the material's mass.  The mass is determined by how many molecules of the material there are, and what elements compose those molecules.

[tinman]

No, a thousand times no.    A mole is a mole is a mole is a mole.  Material state is related to the volume a given mass occupies.  It does not change the material's mass.  The mass is determined by how many molecules of the material there are, and what elements compose those molecules.

Mark-what is mass?
Is it the weigbt an object weighs?

[MarkE]

Mark-what is mass?
Is it the weigbt an object weighs?

First: mass is not weight.  Mass determines:  1) Resistance to acceleration, and 2) Force of acceleration towards other mass separated by a distance.  In proximity to a dominant mass, IE such as anything here on earth relative to the earth, mass will relate to weight:  equivalent force acting on the mass from the acceleration due to gravity by a nearly uniform scalar.  For instance on earth we use Ge as ~9.8 m/s/s.

Second: The weight of a particular number of moles of a given material does not change with phase.  A mole of: ice, water, or steam all have the same mass.  And barring locations with radical gravitational gradients: at any given location they experience the same gravitational force that we describe as weight.

[Qwert]

Mark-what is mass?
Is it the weigbt an object weighs?

https://www.google.com/webhp?sourceid=chrome-instant&rlz=1C1GGGE_plUS353US488&ion=1&espv=2&ie=UTF-8#sourceid=chrome-psyapi2&ie=UTF-8&q=what%20is%20mass%3F

Unless you change the state of that material.
Energy is used to convert the liquid to gas  75% of which is returned when the gas is converted back to liquid. This leaves the onboard turbines a task of generating the remaining25%

No i didnt. I said it takes no energy to turn the gas into liquid And like i said before,when this transition is taking place,energy is returned to the source that created it.

Energy is used to convert the liquid to gas but no energy to turn the gas into liquid.?  What's going on here??

[MarkE]

My understanding of what Tinman is saying is that he does need external energy to condense the gas to liquid.  If one has a heat sink below the phase change temperature for the pressure one is at, then simply cooling the gas and in the process giving up stored energy to the heat sink will condense the gas to liquid.