Catalysts and activation energy
Worksheets and lesson ideas to challenge students aged 11 to 16 to think about catalysts and activation energy (GCSE and Key Stage 3)
Students are used to recalling the definition of a catalyst: “A substance that lowers the activation energy for a reaction by providing an alternative route with a lower activation energy”. But do they understand? These are difficult concepts to master, and the idea that catalysts are not used up is often stated by teachers but rarely shown to students. Students need careful guidance if they are to understand the important differences between kinetics (rate) and thermodynamics (energy and entropy), and why reactions occur in the first place.
Activation energy and understanding energy profile diagrams
GCSE worksheet where students interpret energy profiles. Students work in pairs to compare energy profiles (energy level diagrams) for different reactions. They put these reactions in order, based on their rate of reaction and enthalpy change. Students can also annotate these energy level diagrams to show activation energies and enthalpy changes. (PDF)
The pink catalyst: prove to your students that catalysts are not used up
This demonstration is a very visual way to show how catalysts work. In this reaction, tartrate ions react with hydrogen peroxide to form bubbles of carbon dioxide, according to the equation C4H4O62- + 5H2O2 → 4CO2 + 6H2O + 2OH–.
When these two solutions are initially mixed together they do not appreciably react (show the class). The reaction occurs when cobalt(II) ions are added as the catalyst. Students see how the pink cobalt (II) ions are first oxidised to green (III) ions but then reform at the end of the reaction. More information on how to set up this demonstration of a catalyst.