Some Examples of sublimation Chemistry are the processes that experience water, carbon dioxide, iodine, arsenic Or sulfur.
Sublimation is the process of direct transformation from the solid state to the gaseous state, without passing through a liquid phase. It is an endothermic phase transition that occurs at temperatures and pressures below the triple point of a substance, temperature and pressure in which the three phases coexist (Sublimation (chemistry), 2008).
Figure 1: phase diagram of carbon dioxide.
At a given temperature, most compounds and chemical elements may possess one of three different states of matter at different pressures. In these cases, the transition from the solid state to the gaseous state requires an intermediate liquid state.
At temperatures below the triple point, a decrease in pressure will lead to a phase transition, directly from the solid to the gaseous. Also, at pressures below the pressure of Triple point , An increase in temperature will result in a solid being converted into gas without passing through the liquid region (Boundless, S.F.).
For some substances, such as coal and arsenic, sublimation is much easier than evaporation . This is because the pressure of their triple point is very high and it is difficult to obtain them as Liquids .
The sublimation process requires additional energy; Is an endothermic change. The enthalpy of sublimation (heat of sublimation) can be calculated with the sum of the enthalpy of fusion and the enthalpy of vaporization.
The opposite process, where a gas experiences a phase change in solid form, is called deposition or desublimation (Anne Marie Helmenstine, 2016).
20 examples of sublimation
1- Carbon dioxide
Dry ice is solid carbon dioxide. At room temperature and pressure, it is sublimed into carbon dioxide vapor (Figure 2).
It can be used to create a special smoky or ghostly effect. Because of its relative safety, dry ice is the solid of choice in classroom demonstrations.
Figure 2: Dry ice or solid carbon dioxide.
2- Water
Under special conditions, frozen water (ice) can bypass the liquid phase and sublimate into the air. It is difficult to see the sublimation of the ice, but you can see the results.
The southern surface of Mount Everest has perfect conditions for sublimation of snow: low temperatures, intense sunlight, low relative humidity and dry winds (VanBuren, S.F.).
3- Iodine
Iodine at a temperature of 100 ° C sublimes from a solid to a toxic purple gas. This is used in forensic sciences to capture fingerprints.
4- Arsenic
At 615 ° C, the arsenic sublimates. This represents a hazard given the toxicity of the element.
5- Sulfur
This compound sublimates between 25 and 50 ° C causing toxic and suffocating gases (Tucker, 1929).
6- Printing inks
Dry sublimation printers use the sublimation process to print photographic quality images.
The process begins when there are special films containing solid pigments that when heated, sublimated and subsequently recaptured.
Images can be printed on polyester shirts, aluminum or chrome vessels or sheets (METAL PRINTS DYE-SUBLIMATION ONTO ALUMINUM, S.F.).
7- Aromatizers
Solid air fresheners also sublimate. These compounds are usually esters, including those that hang on the toilet. This is how the chemicals are put directly into the air and make the smell fresh.
8- Naphthalene
Recovered image from Homemade Experiments website.
Mothballs are made with this compound which, when sublimated, distracts moths.
9- Zinc
This compound tends to sublimate at low pressure.
10- Aluminum
This metal is sublimated at temperatures above 1000 ° C for certain industrial processes.
11- Metallurgy
Certain alloys are purified by sublimation methods. In this way, the compounds that make up the alloy are separated, the purified products being obtained.
12- Cadmium
Another compound that sublimates under low pressure. This is especially problematic in situations where high vacuum is worked.
13- Graphite
This material is sublimated by passing a high amperage current in a high vacuum. This procedure is used in transmission electron microscopy to be conductive samples and to have higher resolution.
14- Gold
Gold sublimation is used for the manufacture of low-cost medals and"gold-plated"jewelry. It is also used for the treatment of scanning electron microscopy samples.
15- Camphor
At a certain temperature the camphor sublimates, which is used for its purification or for therapeutic purposes.
16- Menthol
Menthol is very easily sublimated. When you observe a bottle of pure menthol you see fine menthol needles. These grow by deposition. This means that the solid menthol sublimates.
17- Anthracene
It is a white solid that easily sublimates. This method is generally used for purification.
18- Benzoic acid
It is an additive for food that is easily sublimable for its purification (Crampton, 2017).
19- Salicylic acid
It is used as an ointment to relieve fever since it is easily sublimated. This method is also used for purification (Purification of Organic Compounds, S.F.).
20- Cosmic sublimation
The phenomenon of sublimation is not only observed on a daily basis or in the laboratory. Astronomers and astrophysicists tend to deal with this phenomenon as they turn their gaze to the stars.
Examples are the sublimation of water from comet nuclei, the comet's approach to the sun, and the sublimation of polar ice caps on Mars during the Martian summer (Swinburne University of Technology, S.F.).
References
- Anne Marie Helmenstine, P. (2016, June 20). Sublimation Definition (Phase Transition in Chemistry) . Retrieved from thoughtco.com.
- (S.F.). Solid to Gas Phase Transition . Retrieved from boundless.com.
- Crampton, L. (2017, May 5). Health Effects of Benzoic Acid, Sodium Benzoate, and Benzene . Retrieved from caloriebee.com.
- METAL PRINTS DYE-SUBLIMATION ONTO ALUMINUM . (S.F.). Recovered from blazing.com.
- Purification of Organic Compounds . (S.F.). Retrieved from askiitians.com.
- Sublimation (chemistry) . (2008, April 2). Retrieved from newworldencyclopedia.org.
- Swinburne University of Technology. (S.F.). Sublimation . Retrieved from astronomy.swin.edu.au.
- Tucker, R. P. (1929). Notes on the Sublimation of Sulfur between 25 ° and 50 ° C. Eng. Chem., 21 (1) , 44-47.
- VanBuren, J. (S.F.). Examples of sublimation in real life . Retrieved from education.seattlepi.com.