Chemistry Help UKFree A-level chemistry practice

Kinetics simulator

Maxwell–Boltzmann distribution explorer

Change the temperature and activation energy to see how the distribution curve and reacting fraction change. AQA and OCR A views use the emphasis required by each specification.

Peak positionReference position
Peak heightReference height
High-energy tailModelled reacting fraction shown

Interactive graph: change temperature to move the distribution peak and alter the area beyond the activation energy.

Current distribution 300 K reference Activation energy
Modelled fraction at or above Ea—
Most probable energy, Emp—
Mean energy—
At 400 K the teal curve is broader than the 300 K reference. Increase the temperature and watch the peak move right and down while the area beyond Ea increases.
What this visual model represents

The graph uses a normalised Maxwell–Boltzmann-shaped distribution on a relative energy axis. Every temperature curve has the same area. The energy values and reacting fractions are illustrative and do not represent a named gas.

Raising the temperature

  • The distribution becomes broader.
  • The peak becomes lower and moves to higher energy.
  • The total area under the curve stays the same when the number of molecules is unchanged.
  • A greater fraction of molecules has energy equal to or greater than the activation energy.

Adding a catalyst

A catalyst provides an alternative pathway with a lower activation energy. It does not change the Maxwell–Boltzmann distribution, the mean energy or the position of the original activation-energy line.

AQA and OCR A emphasis

AQA questions may refer to the most probable energy and mean energy. OCR A usually focuses on the shape, area, activation energy and the effect of temperature or a catalyst. The board switch changes the default labels; the extra markers remain available.