There are 5 main factors that affect the rate of reaction. 1. Concentration: Increasing the concentration increases the frequency of collisions between particles. 2. Surface Area: Increasing the surface area of a solid. Providing a solid surface for some gas phase reactions can help molecules come together. 3. Temperature: Increasing the temperature increases the amount of collisions between particles, and more particles have energy over that of the activation energy. 4. Pressure: Increasing the pressure has the same effect as concentration; increasing the frequency of collisions. 5. Catalysts increase the proportion of molecules that have energy above the activation energy.