The triple point is defined as the temperature and pressure of a substance, at which its solid, liquid and gaseous phase coexist in complete equilibrium. Now to get back to sublimation, the change from the solid phase to the gas phase occurs at temperature and pressure which are below the triple point.
It is very important to note that the term sublimation is applicable only when a purely physical change of state happens. A chemical reaction resulting in the formation of gas from solid is not sublimation. Ex: We all have seen candles burning. When a candle burns, the paraffin in the candle burns and it is vaporized. This vapor reacts with oxygen in the atmosphere and forms carbon dioxide.
This is NOT sublimation because this happens because of a chemical reaction. A few Examples of Sublimation:. Naphthalene balls used in mothballs readily sublimates at room temperature and pressure. Dry ice which is solid carbon dioxide readily sublimates at room temperature and pressure.
Another term that is relevant to understanding sublimation is "Vapour Pressure". The pressure is exerted by the vapor in thermodynamic equilibrium with its solid or liquid phase at a temperature in a closed system. In simple terms, it relates to the ease with which particles can escape from the solid or liquid phase into the gas phase. A substance which has a high vapor pressure at normal temperatures is called Volatile.
The Process:. When heat energy is absorbed by some of the molecules, they acquire much higher energy than their neighbors and thereby overcome the forces of attraction and escape into the vapor phase. Since this requires additional energy, it is called as an endothermic reaction. The heat or energy required to change the state from solid to gas is called the enthalpy of sublimation and this is unique to each substance.
Relatively, very few solids are capable of sublimation. Hence this process of sublimation can be used as an excellent purification method. When a solid is contaminated with non-volatile impurities then this is a very good method for separation and purification. The contaminated or impure solid is heated in a vessel while keeping it in contact with a cold surface. On heating, the volatile solid sublimes and attaches to the cold surface above it, while the impurities remain below.
This is a very eco-friendly process because this does not use any solvents, or no waste is generated. The limitation is that it is not very efficient in separating volatile solids from one another. In order to effect sublimation, many criteria need to be met. First, the sample should be kept at a sufficient temperature to maintain high vapor pressure, because if it goes below that temperature the material could decompose.
Second, a surface must be available on which the sublimed vapor can condense or solidify. How is Sublimation Different from Evaporation? Chemistry Expert. Helmenstine holds a Ph. She has taught science courses at the high school, college, and graduate levels. Facebook Facebook Twitter Twitter. Updated January 09, Sublimation Definition Sublimation is the transition from the solid phase to the gas phase without passing through an intermediate liquid phase.
Featured Video. Cite this Article Format. Helmenstine, Anne Marie, Ph. Sublimation Definition Phase Transition in Chemistry. What Is a Volatile Substance in Chemistry? Molecular Formula for Common Chemicals. Wood-Burning Stoves. Study now. See Answer. Best Answer.
There are links below to articles on sublimation and pyrolysis. Study guides. Q: When wood burns is that sublimation? Write your answer Related questions. Is burning wood sublimation? What does not undergo sublimation snow iodine wood or dry ice? Which type of wood burns longer? When wood burns chemical energy in the wood is transformed in to what?
What is the process called of wood turn in to ash? What changes occur when wood burns? Which type of wood burns the fastest? Which wood burns the best wood from a store or sticks from trees?
What type of pine wood burns the fastest? Does wood burn or the vapors? What type of wood burns the longest?
Wood in a fireplace or the ashes in the fireplace after the wood burns has more potential energy? Does wood undergo pyrolysis before it burns? Wood burns is a physical property of wood? When wood burns in fire what happens to the wood?
What burns into ash? What burns on a fire? Why does fire burn fast?
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