Use the simulation in your science or Physics class to illustrate specific latent heat
Simulation description
This is a 3D molecular model of water changing state from ice to liquid, driven by a continuous heating model based on AQA GCSE values. Twelve water molecules are arranged in two puckered chair rings — the correct ice Ih geometry, not a flat ring — each oxygen (red) bonded to two hydrogens (cream) with visible covalent bonds, and connected to neighbouring molecules by 24 dashed cyan hydrogen bonds.
Pressing 🔥 Heat On accumulates energy continuously. In the ice warming phase, molecules vibrate with increasing amplitude as temperature climbs from −20°C to 0°C (Q = mcΔT, c = 2 100 J/kg°C). When temperature reaches 0°C, the latent heat phase begins: vibration amplitude locks constant — because kinetic energy is no longer increasing — while the 24 hydrogen bonds begin snapping one by one in a randomised sequence. Each bond that breaks causes the two molecules it connected to gain proportional translational freedom; they begin drifting slowly away from their lattice positions while still-bonded neighbours stay fixed. The temperature display holds at 0°C throughout, and the dot on the temperature graph travels along the flat section in real time. Only when the last bond breaks does temperature start rising again — the dot leaves the flat section, molecules move fully freely, and the formula switches back to Q = mcΔT with c = 4 200 J/kg°C. Pressing ❄ Cool reverses the process: bonds reform, molecules return to lattice positions, and temperature falls back through 0°C. The left-hand panel shows the live temperature, current formula, where the energy is going, and an exact count of intact hydrogen bonds. Jump-to shortcuts (Ice / Melting / Water buttons) let teachers skip to any phase instantly.
Suggested class activity — “When does the temperature start rising again?”
Hook (2 min): Ask pupils: “If I keep adding heat to a beaker of melting ice, when does the water get hotter — straight away, or only after all the ice has melted?” Take a show of hands. Most will say straight away.
Explore (8 min): Pupils open the simulation and press Heat On with the temperature graph and H-Bonds both toggled on. Their task is to watch the graph dot and answer three questions in their books:
- What happens to the molecules’ movement between −20°C and 0°C?
- What happens to the temperature while bonds are breaking? Write down exactly what you see.
- What is different about the molecules’ movement once the last bond has snapped?
Discuss (5 min): Cold-call on question 2. Draw out the key sentence: “Temperature stayed at 0°C because the energy was breaking bonds, not speeding up molecules.” Write it on the board.
Apply (5 min): Give pupils this calculation: A student heats 0.2 kg of ice at 0°C until it has all melted. How much energy was needed? (L = 334 000 J/kg). Answer: Q = 0.2 × 334 000 = 66 800 J. Ask them to compare that to warming the same mass of water by just 1°C: Q = 0.2 × 4 200 × 1 = 840 J. Ask: “Why does melting take nearly 80 times more energy than warming the water by one degree?” The answer is visible in the simulation — 24 bonds all need breaking.
Close (2 min): Return to the opening question. Ask the same show of hands again. Ask a pupil who changed their mind to explain why using the word bonds.