INTERNAL energy...?

[hassam]

plx anybody tell me wats the internal energy.....nd wat does potential enrgy means at molecular level? nd wat ll happen to internal energy of water if some water evaporates at constant temp.?

 

[beacon_of_light]

Internal energy is the sum of random potential and kinetic energies of the atoms in a molecule or a compound.
When water evaporates at a constant temperature, Ke remains constant. But since the water molecules are approaching the free state, Pe increases. Thereby, internal energy increases.
Always remember that the Pe of molecules in binding stage is negative but as bonds break, the molecules approach free state so the Pe becomes zero .i.e increases ( analogous to gravitational potential energy)... max of Pe is zero at free state.
Hope you get that!

 

[hassam]

free state means that there are no intermolecular attraction forces btw molecules ???

 

[beacon_of_light]

yeah

tht the molecules are far apart with no forces of attraction

 

[hassam]

" the molecules approach free state so the Pe becomes zero"
u r talking abt wich molecules.......the one that escaped(high energy molecules) or the ones that remained in the liquid

 

[beacon_of_light]

I am tawking about the gaseous water... water in vapour phase or the ones that escaped. This could be studied generally for all the water moleculaes too since during boiling, temperature does not change which means again phase molecules considered...

 

[Rajendra bogati]

internal energy means the sum of potential and kinetic energy of an atom.....when water evaporates at constant temperature kinetic energy remains constant but potential energy increases bcz height of an atom increases...hence internal energy increases....

 

[usman]

@Rajendra bogati: this seems quite reasonable @ 'when water evaporates at constant temperature kinetic energy remains constant but potential energy increases bcz height of an atom increases'