Hess's Law states that the total enthalpy change for a chemical reaction is the same regardless of the route taken from reactants to products, as long as the initial and final conditions are identical. If a reaction can be written as the sum of several steps, the overall ΔH equals the sum of the ΔH values of those steps.

What do the ΔH sliders in this simulator control?

The ΔH₂ slider sets the enthalpy change of the first step in the indirect two-step pathway, and the ΔH₃ slider sets the enthalpy change of the second step. Both are constrained to a realistic range around their literature values, and the diagram and balance indicator update instantly as you drag them.

What does the Balanced / Unbalanced indicator check?

It compares the fixed literature direct ΔH₁ against the sum of the current ΔH₂ and ΔH₃ values and reports Balanced whenever the two agree to within about half a kilojoule per mole — a live demonstration that Hess's Law holds only when the step enthalpies are the true, correctly measured values.

Home▸Chemistry & Materials▸Hess's Law — Enthalpy of Reaction (2D)

Hess's Law — Enthalpy of Reaction (2D)

2D energy-cycle simulator: pick one of four real thermochemical cycles, drag each step's ΔH on live sliders, and watch the diagram show whether ΔH_direct = ΔH_step1 + ΔH_step2.

Chemistry & Materials2DModerate60 FPS📱 Mobile-adapted⇄ 3D version

This 2D companion draws the same thermochemical energy-level diagram as the 3D version on a plain canvas. Pick one of four real reaction cycles — carbon burning to CO₂ via CO, graphite versus diamond, hydrogen burning via steam, or sulfur oxidizing to SO₃ — then drag the two step sliders to see the indirect amber path visibly separate from the fixed, literature-accurate green direct path whenever the values don't add up, and snap back into balance when they do.

⚙ Under the hood

Pick a real thermochemical cycle, drag each step's ΔH on live sliders, and watch the energy-level diagram confirm or break ΔH_direct = ΔH_step1 + ΔH_step2.

Hess's lawenthalpythermochemistrystate function

2D · HTML5 Canvas 2D · 60 FPS target · runs fully client-side, no install