The reason why Tin granules is mostly used or preferred than
just a piece of Tin because a piece of Tin is plainly metal, in which this will
be difficult in having it to be oxidized when it is exposed or in the air
rather than Tin granules.
The tiny granules are used as they increase the surface-area to volume ratio. Smaller granules have a higher surface area to volume ratio. In a chemical reaction, it means that the reaction increases as there is more particle to particle reaction.
The reaction in which we can't take back the product to reactant form .Or in simple words the reaction which is irreversible is called chemical reaction
Example:-
Burning of wax
We cannot pull back the reaction to get wax back .
