R2.2 How Fast? The Rate of Chemical Change

How can the rate of a reaction be controlled?

R2.2 How fast? The rate of chemical change.pptx

Skills Focus

Experimental Techniques: Measuring variables: understand to accurately measure to an appropriate level of precision: mass, volume, pH and time.
Applying techniques: colorimetry or spectrophotometry
Controlling Variables: calibrate measuring apparatus (calorimeter)
Controlling Variables: maintain constant environmental conditions of systems
Technology: Applying technology to collect data: use sensors.
Technology: Applying technology to process data: represent data in a graphical form.
Graphing: Sketch graphs, with labelled but unscaled axes, to qualitatively describe trends.
Graphing: Construct and interpret tables, charts and graphs for raw and processed data including bar charts, histograms, scatter graphs and line and curve graphs.
Graphing: Extrapolate and interpolate graphs.

UNDERSTANDINGS

R2.2.1—The rate of reaction is expressed as the change in concentration of a particular reactant/product per unit time.
- Determine rates of reaction.
- Calculation of reaction rates from tangents of graphs of concentration, volume or mass against time should be covered.
R2.2.2—Species react as a result of collisions of sufficient energy and proper orientation.
- Explain the relationship between the kinetic energy of the particles and the temperature in kelvin, and the role of collision geometry.
R2.2.3—Factors that influence the rate of a reaction include pressure, concentration, surface area, temperature and the presence of a catalyst.
- Predict and explain the effects of changing conditions on the rate of a reaction.
R2.2.4—Activation energy, Ea, is the minimum energy that colliding particles need for a successful collision leading to a reaction.
- Construct Maxwell–Boltzmann energy distribution curves to explain the effect of temperature on the probability of successful collisions.
R2.2.5—Catalysts increase the rate of reaction by providing an alternative reaction pathway with lower Ea.
- Sketch and explain energy profiles with and without catalysts for endothermic and exothermic reactions.
- Construct Maxwell–Boltzmann energy distribution curves to explain the effect of different values for Ea on the probability of successful collisions.

MAKING CONNECTIONS

Tool 1, 3, Inquiry 2—Concentration changes in reactions are not usually measured directly. What methods are used to provide data to determine the rate of reactions?

Tool 1—What experiments measuring reaction rates might use time as i) a dependent variable ii) an independent variable?

Structure 1.1—What is the relationship between the kinetic molecular theory and collision theory?

Tool 1—What variables must be controlled in studying the effect of a factor on the rate of a reaction?

Nature of science, Tool 3, Inquiry 3—How can graphs provide evidence of systematic and random error?

Reactivity 2.3—What is the relative effect of a catalyst on the rate of the forward and backward reactions?

AHL Structure 3.1—What are the features of transition elements that make them useful as catalysts?