Determine if a substance can skip the liquid phase and transition directly from solid to gas based on pressure conditions and the triple point
See how pressure determines whether a substance melts or sublimes
Enter a substance and ambient pressure to check if direct solid-to-gas transition is possible
Select a substance and enter the ambient pressure to determine if sublimation (solid→gas without liquid) is possible.
Choose from 7 common substances that can undergo sublimation under the right conditions.
Input the ambient pressure in atm, Pa, kPa, or mmHg. Standard atmospheric is 1 atm.
Add current temperature to get additional context about the phase state.
Instantly see if sublimation is possible and why, with a detailed scientific explanation.
A solid can skip the liquid phase and go directly to gas when the ambient pressure is below the substance's triple point pressure. The triple point is where all three phases coexist.
Below the triple point pressure, liquid cannot exist — the substance must either be solid or gas. This is why dry ice (CO₂) always sublimes at sea level: its triple point is at 5.18 atm.
Water's triple point is at 0.006 atm — far below atmospheric pressure. At 1 atm, ice melts into liquid water before becoming gas. Only in vacuum conditions can water ice sublimate.
Freeze-drying works by reducing pressure below water's triple point, forcing ice to sublimate directly. This preserves food structure better than heat drying.
The key factor is whether the ambient pressure is below the substance's triple point pressure. If yes, the liquid phase cannot exist, and heating the solid will cause it to sublimate directly into gas.
CO₂'s triple point pressure is 5.18 atm — much higher than normal atmospheric pressure (1 atm). Since we live below the triple point pressure, liquid CO₂ cannot exist at room conditions, so dry ice always sublimes.
Yes, but only at very low pressures (below 0.006 atm / 611 Pa). This is why freeze-drying chambers use vacuum pumps. In nature, snow sublimation occurs in very cold, dry, windy conditions.
The triple point is the unique temperature and pressure where solid, liquid, and gas phases all coexist in thermodynamic equilibrium. It's a fundamental property of each substance.
The checker uses ideal thermodynamic data from NIST. Real-world sublimation can also depend on humidity, airflow, surface area, impurities, and container geometry. The triple-point check gives the fundamental thermodynamic answer.