Why powdered flour reacts more quickly than lumps of wheats?

The powdered form of food items has larger surface area exposed as compared to larger piece or lump forms. For this reason if we want a food item such as wheat, gram pulses in powdered to get mixed in the liquid quickly to make flour or dough, we prefer them in powdered or grounded from before hand. Hence, powdered flour reacts more quickly rather than the lumps if wheats in various chemical or fermentation reactions.