Enthalpy & Activation Energy Diagram
Drag the reactant, peak and product levels of an energy profile and see ΔH, Ea and the effect of a catalyst.
Drag the three orange handles: the reactant level, the peak (activation energy) and the product level. Turn on the catalyst to lower the peak.
About the Enthalpy & Activation Energy Diagram
Free enthalpy & activation energy diagram. Drag the reactant, peak and product levels of an energy profile and see ΔH, Ea and the effect of a catalyst. Drag, change the sliders and see the result live. No sign-up, works on phone and computer. Built for reactions & kinetics, the enthalpy & activation energy diagram runs instantly in your browser: change a setting or drag an object and the result updates at once, so you learn by trying things out rather than only reading about them.
Drag the reactant, peak and product levels of an energy profile and see ΔH, Ea and the effect of a catalyst. Use it to explore reactions & kinetics ideas at your own pace, then check what you found against the key ideas further down this page.
How to use the Enthalpy & Activation Energy Diagram
- Use the controls to change Activation energy Ea, Enthalpy change ΔH, Catalyst. The simulation reacts instantly.
- Pick an option such as Off, On to switch modes or load an example.
- Press "Roll the ball", "Reset" to start, reset or change what is happening.
- Where you see a glowing handle, object, weight or atom, drag it with your mouse or finger. Everything responds in real time.
- Watch the readouts and graphs update as you experiment, and compare what you see with the key ideas below.
Things to try
- Make ΔH negative, then positive.
- Drag the peak up and roll the ball.
- Turn the catalyst on and compare Ea.
- Set ΔH near zero and see the reaction is thermoneutral.
Key ideas you can learn
- ΔH is the energy of the products minus the energy of the reactants.
- Negative ΔH is exothermic; positive ΔH is endothermic.
- Activation energy is the height of the barrier the reaction must climb.
- A catalyst lowers the barrier for both directions but does not change ΔH.
Where this is used in the real world
Industrial catalysts, hand warmers, cold packs, rocket fuels and the design of every chemical plant depend on energy profiles.
Who is this simulation for?
Students learning reaction rates, equilibrium and equations, and teachers who want a visual way to explain what happens to particles.
For teachers: project it on the board, let students predict what will happen, then run it together. For students: change one thing at a time and write down what changes.
Frequently asked questions
What is activation energy?
The minimum energy that colliding particles need to react, shown as the height from reactants to the peak.
Does a catalyst change ΔH?
No. It only lowers the activation energy, so the reaction is faster but releases or absorbs the same heat.
Is the Enthalpy & Activation Energy Diagram free to use?
Yes. It is completely free, with no signup, no download and no ads inside the simulation. It runs in your web browser.
Does the Enthalpy & Activation Energy Diagram work on a phone or tablet?
Yes. It uses touch as well as the mouse, so you can drag objects with your finger. A larger screen makes the controls easier to see.