Simpler
Simpler
Free · no account · runs in the browser

Simulations you can take apart

Most classroom animations are drawings that move. These compute. Where a simulation can run the real model — actual charges, actual forces, actual equations — it does, and where it cannot, the page says so and says what it used instead.

AP BiologyUnit 1 · Chemistry of life

Water, adhesion, and how a tree drinks

Zoom from a cut plant stem into the wall of a single xylem vessel, drag individual water molecules until they snap hydrogen bonds, then drive capillary rise with vessel diameter, temperature and transpiration until the column cavitates. The molecular stages are a real molecular-dynamics simulation.

  • Polar covalent bonding
  • 104.5° geometry and the molecular dipole
  • Hydrogen bonding
  • Cohesion and adhesion
  • All three van der Waals forces
  • Capillary action and Jurin's law
  • Cohesion–tension theory
Open the simulation2-minute tour · 4 to explore

Four stages

  1. 1The stem· Life size · ≈ 3 mm across
  2. 2The vessel wall· ×1 000 000 · ≈ 5 nm across
  3. 3Molecular sandbox· ×5 000 000 · ≈ 3 nm across
  4. 4Capillary rise· Cohesion–tension · 0 – 3.5 m

Real models where possible

The molecular stages of the water simulation run published force-field parameters and integrate them properly. The hydrogen bonds on screen are detected by the same distance and angle test used on real trajectories, not drawn by hand.

Something to actually do

Every simulation has a control that can break it. Remove the wall’s hydroxyl groups; drag a molecule out of its network; heat a vessel until the water column snaps. A student who can only press play has not been given an experiment.

No account, no network

Everything runs in the browser. Open it on a projector with the wifi off and it still works, and nothing about what a student does is sent anywhere.

Simulations are free to open and free to use in a classroom, whether or not your school runs Simpler. If there is a topic you would use one for, tell us which unit and which misconception it has to fix — get in touch. More are in production.