rate of reactions

temperature

when temperature increases, more particles possess energy greater or equal to the activation energy, and the frequency of effective collisions increases between the reactant particles, hence rate of reaction increases

concentration of reactants

when concentration increases, the number of reactant particles per unit volume increases, and the frequency of effective collisions increases between the reactant particles, hence rate of reaction increases

pressure of GASEOUS reactants

at higher pressure, the gas particles are closer to one another, there are more reactant particles per unit volume, and the frequency of effective collisions increases between the reactant particles, hence rate of reaction increases

particle size of reactants 

when particle size is decreased, the surface area increases, the frequency of effective collisions increases between reactant particles, hence rate of reaction increases

presence of catalyst

catalyst provides an alternative pathway with lower Ea. more reactant particles have energy equal to or greater than lowered Ea. frequency of effective collisions between reactant particles increases, and rate or reaction increases