I'm not sure what you mean by your question because heating the solution will not increase particle size.

But from my limited knowledge, it can be used to

• speed up the reaction rate
• evaporate the aqueous solution so that all you are left with is the precipitate which you can then weigh to find the number of moles

Heating a solution doesn't increase particle size for gravimetric analysis, but it is to remove any water left over from the salt so that you are left with an anhydrous salt.

Water can affect the weight of your precipitate and so that will give you errors in your calculations.