Reversible process. In a reversible process the series of changes carried out on the system during its transformation from initial
to final state may be possibly reversed in an exact manner.
This is possible when the changes are carried out very slowly in many
smaller steps on the system during its change from initial to final state. By
doing so, each of its intermediate state will be in equilibrium with its
surroundings. Under such conditions the initial and final states of the system
become reversible completely.
For example, when ice melts a certain amount of heat is absorbed. The
water formed can be converted back to ice if the same amount of heat is removed
from it. This indicates that many reversible processes are non-spontaneous
An irreversible process is one which cannot be retraced to the initial
state without making a permanent change in the surroundings. Many of the
spontaneous processes are irreversible in nature.
For eg. Biological ageing is an irreversible process. Water flowing down
a hill on its own accord is an irreversible process.
the characteristics of thermodynamically reversible and irreversible processes are
compared as below:
is a slow process going through a series of smaller stages with each stage maintaining equilibrium between the system and surroundings.
reversible process can be made to proceed in forward or backward direction.
driving force for the reversible process is small since the process proceeds in
done in a reversible process is greater than the corresponding work done in
process can be brought
back to the
initial state without making an
change in the adjacent surroundings.
process the system
attains final state from the initial state with a measurable speed.
During the transformation, there is no equilibrium maintained between the
system and surroundings.
process can take place in one direction only.
a definite driving
force required for the
progress of the irreversible process.
done in a irreversible process is always lower than the same kind of work done
in a reversible process.
process cannot be brought
back to its
initial state without making
a change in the