To mark the upper fixed point of a Celsius scale on a thermometer, the thermometer should be placed in
pure melting ice.
steam above pure boiling water at standard atmospheric pressure.
pure distilled water at room temperature.
pure boiling alcohol.
313 exam-style questions on CIE IGCSE Physics 2.2.3a Melting, boiling, condensation and solidification. Each one has a worked solution and a mark scheme showing where the marks go.