An engineer investigates pure substance X in a sealed cylinder fitted with a movable plunger. When solid X is heated, it changes directly into gaseous X without forming a liquid. No substance other than X is detected before or after heating.
The same force is applied to the plunger when X is solid and when X is a gas.
| State of X | Volume before the force is applied (cm3\text{cm}^3cm3) | Volume while the force is applied (cm3\text{cm}^3cm3) |
|---|---|---|
| solid | 2.0 | 2.0 |
| gas | 1500 | 600 |
A student makes this conclusion:
‘X takes up far more space after heating, so each particle of X must have expanded. Something this different from the solid must be a new substance, so the change is chemical.’
Explain why heating changes solid X into gaseous X.
Evaluate the student's conclusion using the particle model and the results in the table.
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.