Nature of science: Theories can be supported or falsified and replaced by new theories-changing the temperature of a reaction has a much greater effect on the rate of reaction than can be explained by its effect on collision rates. This resulted in the development of the Arrhenius equation which proposes a quantitative model to explain the effect of temperature change on reaction rate. (2.5)
Essential idea: The activation energy of a reaction can be determined from the effect of temperature on reaction rate.
The Arrhenius equation uses the temperature dependence of the rate constant to determine the activation energy.
A graph of 1/T against ln k is a linear plot with gradient - Ea / R and intercept, lnA.
The frequency factor (or pre-exponential factor) (A) takes into account thefrequency of collisions with proper orientations.
Analysing graphical representation of the Arrhenius equation in its linear form.
Describing the relationships between temperature and rate constant; frequency factor and complexity of molecules colliding.
Determining and evaluating values of activation energy and frequency factors from data.
Use energy level diagrams to illustrate multi-step reactions showing the RDS in the diagram.
Consider various data sources in using the linear expression
The flashing light of fireflies is produced by a chemical process involving enzymes.
The relationship between the "lock and key" hypothesis of enzymes and the Arrhenius equation.
Topic 6.1-collision theory
Aims 4 and 7: Use of simulations and virtual experiments to study effect of temperature and steric factors on rates of reaction.
Aim 6: Experiments could include those involving the collection of temperature readings to obtain sufficient data for a graph.
Aim 7: Graphing calculators can be employed to easily input and analyse data for Ea and frequency factor values.