  Classical phase transitions, like solid-liquid-gas or order-disorder spin
magnetic phases, are all driven by thermal energy fluctuations by varying the
temperature. On the other hand, quantum phase transitions happen at absolute
zero temperature with quantum fluctuations causing the ground state energy to
show abrupt changes as one varies the system parameters like electron density,
pressure, disorder, or external magnetic field. Phase transitions happen at
critical values of the controlling parameters, such as the critical temperature
in classical phase transitions, and system critical parameters in the quantum
case. However, true criticality happens only at the thermodynamic limit, when
the number of particles goes to infinity with constant density. To perform the
calculations for the critical parameters, finite size scaling approach was
developed to extrapolate information from a finite system to the thermodynamic
limit. With the advancement in the experimental and theoretical work in the
field of ultra-cold systems, particularly trapping and controlling single
atomic and molecular systems, one can ask: do finite systems exhibit quantum
phase transition? To address this question, finite size scaling for finite
system was developed to calculate the quantum critical parameters. Recent
observation of a quantum phase transition in a single trapped 171 Yb ion in the
Paul trap indicates the possibility of quantum phase transition in finite
systems. This perspective focuses on examining chemical processes at ultracold
temperature as quantum phase transitions, particularly the formation and
dissociation of chemical bonds, which is the basic process for understanding
the whole of chemistry
