Answer:
Liquid Paraffin is naturally occurring hydrocarbon. It is obtained during the process of fractional distillation of crude oil. The composition of these oils consists of long chain heavier alkanes hence highly hydrophobic in nature and insoluble in water. Among various types of paraffin oils their are some high boiling point mineral oils. Which upon high heat either decomposes or can catch fire if reached to flash point.
On the other hand water is made up of oxygen and hydrogen atoms. It highly polar in nature and has a low boiling point of 100 °C at sea level.
In laboratories reactions are often carried out using heating baths. These baths contains different heating mediums like paraffin oils, sand, silicons, waxes e.t.c. As different reactions require different temperatures therefore, the most ideal heating medium should have a low melting and high boiling points.
Hence, water having lower boiling point can not be used for reactions which take place above 100 °C and on the other side paraffin oils can be heated to more than 200 °C therefore, they are preferred over water.