Collision lab.

The opening example illustrates carbon reacting with oxygen to form carbon dioxide. The factor comparisons below use a generic, two-dimensional model of initial reaction rate. Coloured circles are schematic reactant particles; solvent particles are omitted. A green flash marks a collision that could form products. Reactants are retained to keep conditions constant, so the counters are successful collision events, not accumulating product molecules.

Counts come from contacts in the animation. The model checks whether each collision has enough energy; a fixed probability represents correct orientation. Numbers and model seconds are for comparisons only, not experimental predictions. The solid keeps the same total area in this 2D view; breaking it increases exposed perimeter, representing increased surface area for equal masses of a real solid. Gas compression is compared at fixed temperature after thermal equilibration; compression heating is not shown.

The concentration–time graphs are a separate illustrative batch model: reactants are consumed, unlike the constant-condition particle animation. Both panels use identical axes. The generic solution/gas reaction is A + B → product, with an assumed rate proportional to both reactant concentrations. For surface area, excess solid A is assumed, with an approximately constant exposed surface during the plotted interval. Curves are teaching examples, not measured data or predictions for a particular substance. The moving dots follow the comparison clock up to 60 model seconds; the full curves remain visible.

Small samples fluctuate. Allow at least 20 model seconds, restart and compare again. Changing a setting restarts both counters for a fair comparison. Slow motion changes playback speed only.

Further reading: OpenStax: concentration and time · RSC: carbon and oxygen · OpenStax: collision theory · Monash University: factors affecting reaction rates.