Answer:
It leads to more frequent collisions, which increase reaction rate
Explanation:
An increase in reactant concentration leads to an increase in reactant particles which increases the number of collision in a reaction and then causes a reaction to proceed faster.
This belief was first suggested by the collision theory which states that for a reaction to occur, the reacting particles must collide with one another. However, further studies show that not all collisions lead to a reaction, and only effective collisions lead to a reaction.
Hence, an increase in reactant concentration increases the frequency of collision which in turn increases the chances of effective collision and subsequently sincreases the reaction rate.