Higher concentrations and pressures increase reaction rates by providing more reactive particles in the same volume, leading to more successful collisions. Smaller particle sizes also increase reaction rates through a greater surface area and contact between particles, again resulting in more successful collisions. Raising the temperature increases reaction rates as it causes particles to move more quickly, providing more energy and successful collisions that surpass the activation energy. Catalysts increase reaction rates by reducing the activation energy needed, allowing for more successful collisions and a faster reaction.