There is an increase in the frequency of particle collisions which leads to the increased rate of the reaction.
<u>Explanation:</u>
Hydrochloric acid reacts faster with the powdered zinc than with the equal mass of zinc strips.
Since the surface area of the Zinc particle increases when it is powdered and has more active spots when compared to less number of active sites in Zinc strips and so the number of collision between the Zinc particles and the particles of Hydrochloric acid also increases and consequently the rate of the reaction also enhances.
So there is an increase in the frequency of particle collisions.
