Core
Energetics: Enthalpy
Slide 28 of 34
Summary
Enthalpy
of a substance is the sum total of all the kinetic and potential energy possessed
by the different components of the substance.
Every
single chemical change is characterized by a spreading out of energy and/or
matter.
When energy spreads out it spreads from the system,
the source, to the surrounding, the sink.
When
matter is spread out, it is brought about by the flow of energy from the surrounding
into the system.
Since, according to the first law of
thermodynamics, energy is conserved there is no net change in the
energy of the universe (which we will have more to say
about later).
A system that doesn’t exchange energy nor matter
with its surrounding is referred to as an isolated system.
One
that exchanges both: open system, while one that exchanges only energy: closed
system.