In: Chemistry
What is the “driving force” for a spontaneous physical or chemical change? In other words, why do spontaneous physical and/or chemical changes occur?
As per the second law of thermodynamics, any physical or
chemical changes in nature will be spontaneous if the total change
in the entropy for that process is greater than zero or it is
positive. Total change in the entropy means, change in entropy of
the system + change in entropy for the surrounding, combined values
must be positive for a spontaneous process.
Entropy indicates the randomness present in the system, it is
measured in terms of heat transfer between the system and
surrounding.
Spontaneous physical or chemical changes occur because they are
self-driven, there is no external agent needed for them, for
example, burning of a candle, falling of water from a height, these
are spontaneous changes occurring in nature,
Hence, the driving force for spontaneous changes is the increase in
total entropy.