What chemicals are in hot chocolate that that make marshmellows dissovle?

Hot Chocolate typically contains cocoa powder, sugar, and milk or water, which create an acidic environment. The marshmallows, primarily made of sugar, Gelatin, and air, dissolve in this environment as the hot liquid breaks down the sugar and melts the gelatin. The heat and moisture from the hot chocolate further accelerate the dissolution process, causing the marshmallows to soften and eventually dissolve.