Compare the partition
Closed walls prevent crossing while particles still move.
Diffusion Window
Open a partition and follow mixing through repeatable random particle steps.
Grades 3–5 · Chemistry
Your goal
Open the window and step random motion until at least 1 particles of each color have crossed to the other half. Mixing may fluctuate.
Reduced motion is on. The controls still update the scene.
Random-motion step 0. Blue particles on the right 0 of 6; amber particles on the left 0 of 6. The closed partition keeps the groups apart despite their motion.
Changing the window starts a repeatable trial. A seeded random walk moves each particle without directed attraction; walls reflect steps. Twelve enlarged particles make fluctuations easy to see. This two-dimensional illustration omits particle collisions and does not measure real diffusion time. One step or ten steps are always available without animation.
Learn with Diffusion Window
Open a window between two groups of particles and advance their random motion one step or ten steps at a time. Diffusion Window helps elementary learners see how mixing can emerge even though particles do not aim toward another color. Blue circles and amber diamonds may cross in either direction, and the crossing counters can rise or fall as the small sample fluctuates. A closed partition provides a useful comparison. Repeatable seeded trials preserve all twelve particles while guided goals encourage patient observation and explanations based on movement.
What to look for
Expect fluctuations
Particles can cross back, so mixing need not increase every step.
Look for random motion
Neither color is attracted to the other; many random steps can spread them out.
For teachers and curious learners
Explain diffusion through random motion rather than directed attraction. Ask students to predict what will happen, change one setting, and explain what they observe. Learn gives a starting point. Practice and Challenge offer new goals with the same scene.
A seeded two-dimensional random walk reflects at walls. Opening or closing the partition starts a repeatable trial. Twelve enlarged particles omit collisions and real molecular timing; trajectories are not directed toward mixing targets.