Beginner Topic 267 of 1102 States of Matter & Solutions
Sublimation
Direct change from solid to gas without passing through the liquid phase.
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In-depth explanation of Sublimation
Sublimation is the direct change of a substance from solid to gas without passing through the liquid phase. It occurs when the vapour pressure of the solid is high enough to reach the external pressure without melting, which happens below the triple point pressure or for solids with high vapour pressures at ordinary conditions. Sublimation absorbs the enthalpy of sublimation, which equals the sum of the enthalpies of fusion and vaporization. Substances that sublime readily include dry ice, iodine and camphor. The process is used to freeze-dry food and to purify compounds.
Going deeper: Sublimation
Key ideas: Enthalpy of sublimation roughly equals ΔHfus + ΔHvap, for water about 51 kJ/mol. Sublimation happens at pressures below the triple point; CO2 triple point is 5.1 atm, so CO2 sublimes at 1 atm. Freeze-drying removes ice by sublimation under vacuum, keeping food structure.
Common mistakes and connections: Students think sublimation requires high temperature; ice sublimes slowly even below 0 C, which dries frozen laundry. Another error is thinking any solid can sublime at 1 atm; most need the pressure below their triple point. Iodine sublimes on gentle heating. Linked to phase diagrams, triple points and purification by sublimation.
Visualization of Sublimation
Sublimation: at low pressure solid CO2 (dry ice) passes directly to gas at -78.5 C and 1 atm because its triple point is above 1 atm. The interactive lesson shows this as a live animation or chart.
Worked example and use case
Dry ice, solid carbon dioxide, sublimes at -78.5°C at 1 atm, so it turns straight into gas without leaving any liquid.
Frequently asked questions about Sublimation
What is Sublimation?
Direct change from solid to gas without passing through the liquid phase.
Is Sublimation a beginner, intermediate or advanced topic?
Sublimation is a beginner topic in States of Matter & Solutions. It needs no earlier chemistry lessons and is a good starting point.
What should I learn before Sublimation?
Study these earlier topics in States of Matter & Solutions first: Enthalpy of Vaporization, Enthalpy of Fusion, Heating Curve.
What comes after Sublimation?
The next topics in States of Matter & Solutions are Deposition and Phase Diagram.
Can I practise Sublimation with quizzes?
Yes. The interactive lesson includes a self-check question on Sublimation, and the States of Matter & Solutions quiz draws on every topic in this area.
Where Sublimation fits in States of Matter & Solutions
Sublimation is topic 48 of 109 in States of Matter & Solutions.