‹ Chemistry simulationsChemistry · A Level 9701 · 23 Chemical energetics (A Level)Six simulations covering Topic 23: a Born-Haber cycle for NaCl, MgCl₂, MgO or CaO built one enthalpy step at a time, with any term set as the unknown and solved; every term in the cycle defined in 3D, from atomisation to lattice energy; three ionic lattices side by side to see how charge and radius set the lattice energy; the solution cycle that links lattice energy and hydration enthalpies to the enthalpy of solution, and why hydration enthalpy follows charge density; a particle view of entropy with the sign of ΔS predicted and then calculated from standard entropies; and the Gibbs equation as a straight line against temperature, with the temperature at which a reaction becomes feasible.
A lattice energy cannot be measured directly, so it is found by going the long way round: turn the elements into gaseous ions one step at a time, then let the ions fall into the lattice. Hess's law says the total must equal the enthalpy of formation. Build the cycle for one compound, decide which term is the unknown, and let the diagram close.
Every arrow in a Born-Haber cycle has a definition that the exam expects word for word. Pick a term and watch the change it describes: a metal lattice breaking into single atoms, a molecule splitting, an electron leaving or arriving, and finally gaseous ions collapsing into a crystal.
Lattice energy is electrostatic: the attraction between ions grows with the charges and shrinks as the ions get larger and their centres move apart. Compare three rock-salt lattices drawn with the real ionic radii and read the lattice energies beside them.
Dissolving an ionic solid is a tug of war. Energy must be supplied to pull the lattice apart, and energy is released when each gaseous ion is surrounded by water molecules. The enthalpy of solution is the difference. Pick a salt to see the triangle, then switch to the hydration view to see why small, highly charged ions release the most.
Entropy measures how many ways the particles and their energy can be arranged. Gases have far more ways than liquids, and liquids more than solids, so any change that frees particles or makes more gas molecules has a positive ΔS. Predict the sign from the picture, then check it with standard entropy data.
A reaction is feasible when ΔG = ΔH − TΔS is negative. Plot ΔG against T and the equation is a straight line with intercept ΔH and gradient −ΔS, so the sign of ΔS decides whether heating helps or hinders. Drag the sliders, or load a real reaction, and find the temperature where the line crosses zero.
Six interactive simulations for Cambridge A Level Chemistry 9701 topic 23 Chemical energetics: a Born-Haber cycle builder for sodium chloride, magnesium chloride, magnesium oxide and calcium oxide that draws the energy-level diagram step by step from real data and solves whichever term you set as the unknown, 3D definitions of atomisation enthalpy, ionisation energy, electron affinity, lattice energy and enthalpy of formation, a three-lattice comparison showing how ionic charge and ionic radius control the size of the lattice energy, a solution cycle giving the enthalpy of solution from lattice energy and hydration enthalpies with a charge-density view of hydration, an animated particle picture of entropy change with standard entropy calculations, and a Gibbs free energy line against temperature with the crossing temperature for calcium carbonate decomposition.
Six simulations covering Topic 23: a Born-Haber cycle for NaCl, MgCl₂, MgO or CaO built one enthalpy step at a time, with any term set as the unknown and solved; every term in the cycle defined in 3D, from atomisation to lattice energy; three ionic lattices side by side to see how charge and radius set the lattice energy; the solution cycle that links lattice energy and hydration enthalpies to the enthalpy of solution, and why hydration enthalpy follows charge density; a particle view of entropy with the sign of ΔS predicted and then calculated from standard entropies; and the Gibbs equation as a straight line against temperature, with the temperature at which a reaction becomes feasible.
Chemical energetics (A Level) is a free, browser-based simulation for Cambridge International AS & A Level Chemistry 9701 (topic 23 Chemical energetics, sections 23.1 Lattice energy and Born–Haber cycles, 23.2 Enthalpies of solution and hydration, 23.3 Entropy change, ΔS). The course is assessed in Paper 1 (Multiple Choice (AS)), Paper 2 (AS Structured), Paper 3 (Advanced Practical), Paper 4 (A Level Structured), Paper 5 (Planning, Analysis, Evaluation). Syllabus for examination in 2025-2027. There are 6 tabs, each a self-contained experiment with its own controls and live readings, and nothing to install: it runs on a laptop, tablet or classroom projector.
Full syllabus map: A Level Chemistry 9701 topic 23.
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