Question

A doctor applied surgical bandages on the fractured bones of a patient after making them wet. What changes are likely to occur?

Answer 1

1. The surgical bandages which are used on the fractured bones are made up of Plaster of Paris.
2. Plaster of Paris$\left({\mathrm{CaSO}}_4·\frac{1}{2}{\mathrm{H}}_2\mathrm{O}\right)$ is a compound that is made by heating gypsum$\left({\mathrm{CaSO}}_4·2{\mathrm{H}}_2\mathrm{O}\right)$ at a very high temperature nearly about 373K.
3. It is made wet before applying to the fractured bones because when it is mixed with a certain quantity of water it changes into gypsum and Gypsum has a hardening property.

${\mathrm{CaSO}}_4·\frac{1}{2}{\mathrm{H}}_2\mathrm{O}+\frac{3}{2}{\mathrm{H}}_2\mathrm{O}\stackrel{}{\to }{\mathrm{CaSO}}_4·2{\mathrm{H}}_2\mathrm{O}$

Thus, surgical bandages become harder when they wet.