Answer: A cold compress used by athletes is an endothermic reaction.
Step-by-step explanation:
A pack of cold compress used by athletes contains water that holds another bag or tube inside it which is filled with ammonium nitrate fertilizer.
So, on hitting the cold compress the tube breaks down due to which fertilizer gets mixed with water. This mixture absorbs the heat when placed on the area of body having pain, strain or bump.
As a result, we tend to feel cold at the affected area of our body.
Thus, we can conclude that a cold compress used by athletes is an endothermic reaction.