Year 11 / Heating processes
Energy enters. Temperature waits.
During melting or boiling of a pure substance at fixed pressure, energy can change intermolecular potential energy while temperature remains constant. Both phases coexist on the plateau.
Q = mL gives the energy of a complete phase change. For a multistage process, add the energy for warming, changing state and warming again. A constant-temperature phase change does not mean energy transfer has stopped.
Melting ice
Explore the relationship
Ice begins at −20 °C. c(ice) = 2050, c(water) = 4180 J kg⁻¹ K⁻¹; L = 334 kJ kg⁻¹. Curve ends before boiling.
Temperature / °C
Tap or focus a plotted point to read its values.
View plotted data as a table
| Series | Energy / kJ | Temperature / °C |
|---|---|---|
| Temperature / °C | 0 | -20 |
| Temperature / °C | 1.25 | -16.9512 |
| Temperature / °C | 2.5 | -13.9024 |
| Temperature / °C | 3.75 | -10.8537 |
| Temperature / °C | 5 | -7.80488 |
| Temperature / °C | 6.25 | -4.7561 |
| Temperature / °C | 7.5 | -1.70732 |
| Temperature / °C | 8.75 | 0 |
| Temperature / °C | 10 | 0 |
| Temperature / °C | 11.25 | 0 |
| Temperature / °C | 12.5 | 0 |
| Temperature / °C | 13.75 | 0 |
| Temperature / °C | 15 | 0 |
| Temperature / °C | 16.25 | 0 |
| Temperature / °C | 17.5 | 0 |
| Temperature / °C | 18.75 | 0 |
| Temperature / °C | 20 | 0 |
| Temperature / °C | 21.25 | 0 |
| Temperature / °C | 22.5 | 0 |
| Temperature / °C | 23.75 | 0 |
| Temperature / °C | 25 | 0 |
| Temperature / °C | 26.25 | 0 |
| Temperature / °C | 27.5 | 0 |
| Temperature / °C | 28.75 | 0 |
| Temperature / °C | 30 | 0 |
| Temperature / °C | 31.25 | 0 |
| Temperature / °C | 32.5 | 0 |
| Temperature / °C | 33.75 | 0 |
| Temperature / °C | 35 | 0 |
| Temperature / °C | 36.25 | 0 |
| Temperature / °C | 37.5 | 0 |
| Temperature / °C | 38.75 | 0 |
| Temperature / °C | 40 | 0 |
| Temperature / °C | 41.25 | 0 |
| Temperature / °C | 42.5 | 0 |
| Temperature / °C | 43.75 | 0 |
| Temperature / °C | 45 | 0 |
| Temperature / °C | 46.25 | 0 |
| Temperature / °C | 47.5 | 0 |
| Temperature / °C | 48.75 | 0 |
| Temperature / °C | 50 | 0 |
| Temperature / °C | 51.25 | 0 |
| Temperature / °C | 52.5 | 0 |
| Temperature / °C | 53.75 | 0 |
| Temperature / °C | 55 | 0 |
| Temperature / °C | 56.25 | 0 |
| Temperature / °C | 57.5 | 0 |
| Temperature / °C | 58.75 | 0 |
| Temperature / °C | 60 | 0 |
| Temperature / °C | 61.25 | 0 |
| Temperature / °C | 62.5 | 0 |
| Temperature / °C | 63.75 | 0 |
| Temperature / °C | 65 | 0 |
| Temperature / °C | 66.25 | 0 |
| Temperature / °C | 67.5 | 0 |
| Temperature / °C | 68.75 | 0 |
| Temperature / °C | 70 | 0 |
| Temperature / °C | 71.25 | 0 |
| Temperature / °C | 72.5 | 0 |
| Temperature / °C | 73.75 | 0 |
| Temperature / °C | 75 | 0 |
Explore: Change sample mass and compare the width of the melting plateau.
Melt 0.10 kg of ice already at 0 °C; L = 3.34 × J kg⁻¹.
- Q = 0.10 × 3.34 × .
- Q = 33 400 J; no warming term is needed.
Assumed knowledge
Energy conservation.
Learning checkpoints & source
YOUR LEARNING CHECKPOINT- Interpret plateaus on a heating curve.
- Combine sensible heat and latent heat.
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