Beyond Static Stoichiometry: A Stochastic Lattice Model for Visualizing Kinetic Constraints in H2–O2 Combustion

Abstract The ″Fire Triangle″ ─ fuel, oxygen, and an ignition source ─ has long functioned as a foundational pedagogical framework in chemistry education; however, its sufficient-condition interpretation leads students to overlook the physical constraints unique to premixed gas-phase combustion, constituting a source of systematic overgeneralization. This paper introduces a stochastic lattice model, grounded in percolation theory, designed to visualize the ″kinetic connectivity″ required for chain reaction propagation in premixed H2(g)–O2(g) combustion. Propagation is represented as connectivity among lattice sites holding both gases, governed by the active-site density (the fraction of sites occupied by both gases, PH·PO), so students can investigate the physical origins of flammability limits and connect the symbolic representation (the balanced equation) with the sub-microscopic picture of individual particles reacting. Monte Carlo sampling (6000 trials per active-site-density point) shows a sigmoidal connectivity transition; when reduced to standard rules it recovers the known 2-D square-lattice site-percolation threshold (pc ≈ 0.593). An exploratory implementation with 18 preservice chemistry teachers using an earlier prototype showed gains across all three assessment items (Q1: 16.7% → 94.4%; Q2: 27.8% → 88.9%; Q3: 11.1% → 83.3%); these data are reported as preliminary context rather than as an efficacy test of the revised simulation. The tool offers a way to teach stoichiometric and spatial-connectivity reasoning as complementary pedagogical perspectives ─ chemical composition and physical connectivity ─ understanding premixed gas-phase combustion as emergent, probabilistic processes.