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9701 AS Chemistry/ Topic 8 Reaction kinetics/ 5 interactive simulations/ drag to rotate 3D scenes

Reaction kinetics, made interactive

Five simulations covering Topic 8: collision theory with successful collisions flashing in 3D, the Boltzmann distribution and the fraction of molecules above the activation energy, measuring a rate from a gas-volume experiment with a tangent tool, how heterogeneous, homogeneous and enzyme catalysts work, and the reasons behind each rate factor.

1. Collision theory 3D · 8.1

Particles must collide, with enough energy and the right orientation, to react. Raise the temperature or the concentration and watch the successful collisions come faster. Every flash is a collision with at least the activation energy.

drag to rotate · flashes are successful collisions

Conditions

4
40
6
COLLISIONS PER SECOND
SUCCESSFUL PER SECOND
FRACTION WITH E ≥ Ea
RATE (RELATIVE)

2. The Boltzmann distribution 2D · 8.1

At any temperature the molecules have a spread of energies. Only those beyond the activation energy can react: the shaded tail. Warm the gas a little and the tail grows a lot; add a catalyst and the line moves left instead.

Distribution

300 K
300 K reference
80
FRACTION ABOVE Ea
VS REFERENCE
The area under each curve is the same (the same total number of molecules). The peak moves right and drops as T rises; the curve starts at the origin and never quite reaches the axis at high energy.

3. Measuring a rate: magnesium and acid 2D · 8.1

Mg + 2HCl → MgCl₂ + H₂. Collect the hydrogen in a gas syringe and plot volume against time. The gradient is the rate: steep at the start, flattening as the acid is used up. Change one factor at a time and compare the curves.

Conditions

1.0 mol dm⁻³
20 °C
10 s
GRADIENT = RATE
INITIAL RATE

4. How catalysts work 3D · 8.1

A catalyst provides an alternative route with a lower activation energy and is not used up. A heterogeneous catalyst works on its surface: molecules stick, their bonds weaken, they react and the products leave. A homogeneous catalyst reacts and is regenerated. Enzymes are proteins that do the same with exquisite selectivity.

drag to rotate · press Run

Catalyst

5. Factors that change the rate: the reasons 2D · 8.1

Each factor works through collision theory. Pick one and see what it changes: how often the particles collide, how energetic the collisions are, or the activation energy itself.

Factor

COLLISION FREQUENCY
ENERGY OF COLLISIONS
ACTIVATION ENERGY
EFFECT ON RATE
TheLucidSTEM · Cambridge International AS Level Chemistry 9701 · Topic 8 Reaction kinetics. Every scene runs in the browser; drag to rotate 3D scenes, wheel to zoom. Values are standard textbook data rounded for teaching.

About this lab: Reaction kinetics

Collision theory in 3D with successful collisions flashing, the Boltzmann distribution and the fraction of molecules above the activation energy, a magnesium and acid rate experiment with a tangent tool, heterogeneous, homogeneous and enzyme catalysis in 3D, and the collision-theory reason behind each rate factor.

Five simulations covering Topic 8: collision theory with successful collisions flashing in 3D, the Boltzmann distribution and the fraction of molecules above the activation energy, measuring a rate from a gas-volume experiment with a tangent tool, how heterogeneous, homogeneous and enzyme catalysts work, and the reasons behind each rate factor.

Reaction kinetics is a free, browser-based simulation for Cambridge International AS & A Level Chemistry 9701 (topic 8 Reaction kinetics, section 8.1 Rate of reaction). The same ideas are examined in Cambridge IGCSE Chemistry 0620 (topic 6 Chemical reactions). The course is assessed in Paper 1 (Multiple Choice (AS)), Paper 2 (AS Structured), Paper 3 (Advanced Practical), Paper 4 (A Level Structured), Paper 5 (Planning, Analysis, Evaluation). Syllabus for examination in 2025-2027. There are 5 tabs, each a self-contained experiment with its own controls and live readings, and nothing to install: it runs on a laptop, tablet or classroom projector.

Syllabus coverage

Full syllabus map: AS Level Chemistry 9701 topic 8.

How to use this simulation

  1. 1. Collision theory. Particles must collide, with enough energy and the right orientation, to react.
  2. 2. The Boltzmann distribution. At any temperature the molecules have a spread of energies.
  3. 3. Measuring a rate: magnesium and acid. Mg + 2HCl → MgCl₂ + H₂.
  4. 4. How catalysts work. A catalyst provides an alternative route with a lower activation energy and is not used up.
  5. 5. Factors that change the rate: the reasons. Each factor works through collision theory.
  6. The buttons at the end of the tab strip give the scene the whole window (Full screen, Hide controls) and, on a dark stage, a projector-friendly palette (Light scene). Many scenes also have drag handles: drag them to change the set-up directly.

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