Answer:
Oceanic & Continental Plates
The oceanic plate is denser and sinks due to its lower buoyancy. It's sucked into the asthenosphere and is melted deeper into the Earth, called a subduction zone. The continental plate is less dense and floats over the top of it since it is more buoyant
Explanation:
Tollens' reagent is prepared by using two-step process : -
Step 1:
Silver oxide is formed by mixing aqueous silver nitrate with base like sodium hydroxide. The reaction is shown below as:

Step 2
Ammonia solution is drop-wise added until all the silver oxide dissolves to form the reagent. The reaction is shown below as:

That would be an endothermic reaction! :)