The physical phenomenon responsible for both increased concentration and increased temperature leading to faster reaction rates is the increased frequency of collisions between reactant molecules.

Here's a breakdown:

* Concentration: When you increase the concentration of reactants, you essentially pack more molecules into the same space. This means there are more opportunities for collisions between the reactant molecules. More collisions translate to a higher chance of successful collisions (those that lead to product formation), resulting in a faster reaction rate.

* Temperature: Increasing the temperature gives molecules more kinetic energy, causing them to move faster and collide more frequently. Furthermore, the higher energy also means that more collisions will have sufficient energy to overcome the activation energy barrier and form products. This combination of increased frequency and higher energy collisions leads to a faster reaction rate.

In essence, both increased concentration and temperature lead to more frequent and more energetic collisions, which are the driving force behind chemical reactions.