The area that deals with the mechanism, the rate, and the energy transfer that occurs when matter undergoes a change
a. analytical chemistry
b. physical chemistry
c. pure chemistry
d. organic chemistry

Physical chemistry is the area that deals with the mechanisms, the rate, and the energy transfer that occurs when matter undergoes a change. So the correct option for the given question is option “B”. Whenever there is a change in the state of matter, the physical properties definitely undergo a change. A solid matter will always have a definite shape and volume, while a liquid has a definite volume but no shape. Gases do not have either definite volume or shape. Chemical properties might not be affected, but physical properties are definitely impacted when a matter undergoes change.

Gallium melts near room temperature and has one of the largest  liquid  ranges of any metal, so it has found use in high temperature thermometers.