Relationship To Heat
In order to discuss the relation between the enthalpy increase and heat supply we return to the first law for closed systems: dU = δQ - δW. We apply it to the special case that the pressure at the surface is uniform. In this case the work term can be split in two contributions, the so-called pV work, given by -pdV (where here p is the pressure at the surface, dV is the increase of the volume of the system) and other types of work δW ' such as by a shaft or by electromagnetic interaction. So we write δW = -pdV+δW '. In this case the first law reads
or
From this relation we see that the increase in enthalpy of a system is equal to the added heat
provided that the system is under constant pressure (dp = 0) and that the only work done by the system is expansion work (δW ' = 0)
Read more about this topic: Enthalpy
Famous quotes containing the words relationship to, relationship and/or heat:
“Artists have a double relationship towards nature: they are her master and her slave at the same time. They are her slave in so far as they must work with means of this world so as to be understood; her master in so far as they subject these means to their higher goals and make them subservient to them.”
—Johann Wolfgang Von Goethe (1749–1832)
“Poetry is above all a concentration of the power of language, which is the power of our ultimate relationship to everything in the universe.”
—Adrienne Rich (b. 1929)
“I have a blood bolt
and I have made it mine.
With this man I take in hand
his destiny and with this gun
I take in hand the newspapers and
with my heat I will take him.”
—Anne Sexton (1928–1974)