To investigate several effects believed to influence rate of reaction, concentration of a substance and temperature, and observe the effects.
Concentration and temperature will both increase the rate of reaction in accordance with collision theory.
The reaction rate or rate of reaction for a reactant or product in any given reaction can be defined as the speed with which a reaction occurs. For example, the oxidation of iron (rusting) is a slow reaction which can take many years, but explosive combustion, such as the ignition of fuel, can take as little as fractions of a second to complete. Dealing closely with reaction rates is collision theory. First proposed in 1916, collision theory describes qualitatively how and why chemical reactions occur, and how the rate of reactions differs from reaction to reaction. It theorises that, for a reaction to occur, the reactant particles must collide, but only a fraction of the total collisions cause actual transformations of reactant molecules into products. This is because only a fraction of the molecules has sufficient energy and the right orientation at the time of impact to break the existing bonds and form new bonds. According to this theory, the two factors which most determine and affect reaction rate are temperature and concentration, the two controllable variables that will be altered and the effects of the changing of which observed in this experiment. Increase in concentration of reactants increases the collision frequency between the reactants. An increase in temperature not only increases the average speed of the reactant particles, therefore also increasing the number of collisions, but also the fraction of particles having kinetic energy higher than the activation energy. Thus the reaction will occur at a higher rate.
See pages 425 and 427 of Q Chemistry, experiments 26.3 and 26.4 respectively.