American Board of Surgical Assistants (ABSA) Orthopedic Practice Test

What is the indication of an exothermic reaction in plaster of Paris?

1. The cast remains cold

2. The cast gets hot

3. The drying time is extended

4. The mixture needs additional water

The correct answer is: The cast gets hot

An exothermic reaction is characterized by the release of heat during the process. In the context of plaster of Paris, when it is mixed with water, it undergoes a chemical reaction that produces heat as it hardens. This heat generation causes the cast to become warm to the touch, indicating that the reaction is exothermic. The production of heat is a key indicator that the chemical reaction is occurring effectively. The intensity of the heat can also be used to deduce the progress of the setting process; a warm cast signifies that the plaster is hardening and solidifying properly. This is why the correct answer identifies that the cast gets hot as a manifestation of the exothermic reaction taking place during the hardening of plaster of Paris.