i dont know to explain it with cientist terms, or chemistry but to put it simple, is like a powder you put inside your mouth and starts "exploding" i mean, with a tingling sensation, and is like an urban myth that if you eat poprocks and drink coke you will die, or choke yourself to die and the worst possible way (rofl) but really dont go that far, it was explained in myth busters. and in youtube there are ppl that tries that, and, well.... is just and urban myth but very funny...
i think with mentos have the same reaction that with poprocks.