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9701 AS Chemistry/ Topic 5 Chemical energetics/ 5 interactive simulations/ drag to rotate 3D scenes

Chemical energetics, made interactive

Five simulations covering Topic 5: enthalpy profile diagrams with activation energy and catalysts, calorimetry experiments you run and calculate, bond energies with molecules breaking and forming in 3D, Hess's law cycles, and the standard enthalpy definitions with their equations.

1. Enthalpy profile diagrams 2D · 5.1

A reaction profile plots enthalpy against the progress of the reaction. The height of the hump is the activation energy; the difference between the two flat levels is ΔH. Exothermic reactions finish lower than they start. A catalyst provides a lower hump without changing ΔH.

Shape the profile

−90 kJ mol⁻¹
120 kJ mol⁻¹
TYPE
Ea OF REVERSE REACTION

2. Measuring an enthalpy change: calorimetry 2D · 5.2

The energy released or absorbed by a reaction is measured from the temperature change of a known mass of water: q = mcΔT. Divide by the amount reacting to get ΔH per mole. Run each experiment, read the thermometer, and follow the calculation.

Experiment

TEMPERATURE
ΔT
q = mcΔT
ΔH PER MOLE

3. Bond energies: breaking costs, making pays 3D · 5.1

Breaking bonds takes in energy; forming bonds gives it out. ΔH is the energy needed to break all the reactant bonds minus the energy released when the product bonds form. Watch the reactant molecules come apart and the products assemble.

drag to rotate · press Run to break and make the bonds

Reaction

ΔH = Σ(bonds broken) − Σ(bonds made)
Mean bond energies are averages over many compounds, so ΔH from bond energies is only approximate and applies to gaseous species.

4. Hess's law and enthalpy cycles 2D · 5.2

The enthalpy change of a reaction is the same whichever route is taken from reactants to products. That lets you find an enthalpy change you cannot measure directly from ones you can. Follow the arrows round the cycle.

Cycle

RESULT

5. Standard enthalpy changes: definitions and equations 5.1

Each standard enthalpy change has a precise definition that fixes the equation, including the amounts and the states. Pick one and check the equation, the conditions and the sign you should expect.

Enthalpy change of

DEFINITION
SIGN
TYPICAL VALUE

Example equation

Standard conditions: 298 K, 100 kPa, every substance in its standard state, solutions at 1 mol dm⁻³. The symbol ⦵ marks a standard value.
TheLucidSTEM · Cambridge International AS Level Chemistry 9701 · Topic 5 Chemical energetics. Every scene runs in the browser; drag to rotate 3D scenes, wheel to zoom. Values are standard textbook data rounded for teaching.

About this lab: Chemical energetics

Enthalpy profile diagrams with activation energy and catalysts, calorimetry experiments with q = mcΔT, bond energies with 3D molecules breaking and forming, Hess's law enthalpy cycles, and the standard enthalpy change definitions with their equations.

Five simulations covering Topic 5: enthalpy profile diagrams with activation energy and catalysts, calorimetry experiments you run and calculate, bond energies with molecules breaking and forming in 3D, Hess's law cycles, and the standard enthalpy definitions with their equations.

Chemical energetics is a free, browser-based simulation for Cambridge International AS & A Level Chemistry 9701 (topic 5 Chemical energetics). The same ideas are examined in Cambridge IGCSE Chemistry 0620 (topic 5 Chemical energetics). 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 5 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.

Syllabus coverage

Full syllabus map: AS Level Chemistry 9701 topic 5.

How to use this simulation

  1. 1. Enthalpy profile diagrams. A reaction profile plots enthalpy against the progress of the reaction.
  2. 2. Measuring an enthalpy change: calorimetry. The energy released or absorbed by a reaction is measured from the temperature change of a known mass of water: q =...
  3. 3. Bond energies: breaking costs, making pays. Breaking bonds takes in energy; forming bonds gives it out.
  4. 4. Hess's law and enthalpy cycles. The enthalpy change of a reaction is the same whichever route is taken from reactants to products.
  5. 5. Standard enthalpy changes: definitions and equations. Each standard enthalpy change has a precise definition that fixes the equation, including the amounts and the states.
  6. The buttons at the end of the tab strip give the scene the whole window (Full screen, Hide controls) and, on a dark stage, a projector-friendly palette (Light scene). Many scenes also have drag handles: drag them to change the set-up directly.

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