A laboratory has three pure substances. The reference values were measured at the pressure used in the experiment.
| Substance | Melting point (∘C^\circ\mathrm{C}∘C) | Boiling point (∘C^\circ\mathrm{C}∘C) |
|---|---|---|
| J | -18 | 44 |
| K | 44 | 91 |
| L | 91 | 137 |
Two unlabelled samples, X and Y, are cooled steadily from the gas state until each sample is solid. During each change of state, the temperature remains constant. The constant-temperature stages are listed in the order in which they occur.
| Sample | First constant temperature (∘C^\circ\mathrm{C}∘C) | Second constant temperature (∘C^\circ\mathrm{C}∘C) |
|---|---|---|
| X | 137 | 91 |
| Y | 91 | 44 |
Use the data to identify X and Y and explain your choices, including why neither sample is J.
The cooling is interrupted when both samples reach 110 ∘C110\,^\circ\mathrm{C}110∘C. State the physical state of each sample at this temperature. Explain your answers using the data.
Describe the arrangement and movement of the particles in each sample immediately after its change of state at 91 ∘C91\,^\circ\mathrm{C}91∘C is complete and cooling continues.
93 exam-style questions on OCR GCSE Chemistry 1.1 The particle model, covering 1.1.1 The particle model and changes of state and 1.1.2 Limitations of the particle model. Each one has a worked solution and a mark scheme showing where the marks go.