Activation Energy Landscape

Activation Energy Landscape transforms the textbook 2D reaction coordinate diagram into a dynamic 3D potential-energy mountain pass. Reactant spheres in the left valley draw thermal kinetic energies scaled by Temperature and attempt to climb over the transition-state saddle (activated complex) into the product valley on the right. Molecules with kinetic energy below the effective activation energy (Ea) roll back into the reactant valley, whereas energetic molecules surmount the peak and turn golden as products. Students can drag the glowing purple transition-state peak vertically, vary ΔH from strongly exothermic (-60 kJ/mol) to endothermic (+60 kJ/mol), or engage the green Platinum catalyst block to lower the barrier by nearly half and watch the reaction rate surge.

• Drag the purple Transition State peak upward to increase Uncatalyzed Ea to 110 kJ/mol and observe how most blue reactant spheres roll back down without reacting.
• Click the green Catalyst block (or toggle Catalyst pathway) and watch the mountain pass drop while the red reference curve remains at the original uncatalyzed height.
• Raise the Temperature slider from 260 K to 580 K and observe how the percentage of successful collisions climbs exponentially according to the Arrhenius equation.
• Slide Enthalpy ΔH from -45 kJ/mol (Exothermic, low product valley) to +45 kJ/mol (Endothermic, high product valley) and verify that the catalyst changes Ea without altering ΔH.
• Press Launch Reactant Wave to send a burst of high-energy colliding molecules across the transition state.

1. 1Define activation energy (Ea) and transition state (activated complex) on a potential-energy reaction coordinate diagram.
2. 2Explain how increasing temperature increases reaction rate by raising the fraction of collisions with energy greater than or equal to Ea.
3. 3Describe how a catalyst increases both forward and reverse reaction rates by providing an alternative pathway with lower activation energy.
4. 4Distinguish between exothermic (negative ΔH) and endothermic (positive ΔH) potential-energy profiles and explain why a catalyst does not change ΔH.

Questions teachers ask