What is sublimation?

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caledon | High School Teacher | (Level 3) Senior Educator

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Sublimation is a description of the way that matter behaves under certain circumstances.

First, we're talking about thermodynamics and states of matter.

Thermodynamics is a way of talking about heat. It describes the way that heat energy flows in a system, such as a bowl of water. 

You've probably heard of states of matter, like solids, liquids and gases. You also know that the same material, like water, can exist in all three states (ice, liquid water and steam). This is because of thermodynamics; the state of the matter depends upon the heat energy that it has. This is why things have boiling and melting points.

The reason that there are specific melting and boiling points also has to do with energy, but this time we have to think atomically; on the molecular scale, there are bonds holding different molecules together. These bonds can be broken if you add enough heat energy. When you add enough heat energy to ice, it melts. When you add more energy to liquid water, it vaporizes.

However, under the right circumstances of pressure and heat, you can actually get a solid to completely skip the liquid step and go straight to being a gas. This is sublimation.

The most common demonstration of sublimation is dry ice, which is just frozen carbon dioxide. The wispy "smoke" that you see coming off of the dry ice is the carbon dioxide sublimating.

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rachellopez | Student, Grade 12 | (Level 1) Valedictorian

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The chemistry definition for sublimation is the transition from from a solid to a gas. This refers to a substance or object that changes its state of matter from a solid state to a gas state. The object does not enter a liquid state during this transformation. An example would be dry ice, which is a solid, but at room temperature it turns to a vapor.

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tonys538 | Student, Undergraduate | (Level 1) Valedictorian

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All substance can exist in three different states given the temperature and pressure they are placed in. The following figure illustrates the state change for a generic substance. The fusion line is one across which the substance changes from liquid to solid. The vaporization line is one across which the state changes from vapor to liquid and the sublimation line is one across which the state changes from gas to solid.

When ice is heated it first melts to water and then evaporates to water vapor. This is due to the commonly prevailing temperature-pressure characteristics. If the pressure were reduced substantially and it is possible for ice to directly sublime to water vapor. Carbon dioxide is a substance that exhibits sublimation at room temperature and normal pressure. It should be kept in mind though that sublimation is just a phenomenon where the state change is from solid to gas. This is possible to achieve with any substance.

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udonbutterfly | Student, College Freshman | (Level 1) Valedictorian

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Sublimations describes the process of a solid that goes directly to the gas phases. This is a physical change since the element is not changing its chemical composition but only its phase. A great example of sublimation would be dry ice. You can usually see in demonstrations where dry ice is used that it goes directly from being an ice, solid, to a vapor, gas.

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atyourservice | Student, Grade 11 | (Level 3) Valedictorian

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Sublimation is the transformation of a solid to gas without going through the liquid phase. It occurs at temperatures and pressures below a substance's triple point in its phase diagram.

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malkaam | Student, Undergraduate | (Level 1) Valedictorian

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Sublimation is phase transition like freezing or melting, but unlike freezing and melting, in which water is turned to ice or ice to water, sublimation is the transformation of solid to gas without passing through the intermediary phase i.e liquid. This occurs at temperatures or pressures below an object's triple point. Example: this happens to dry ice which at a certain temperature becomes gas. I'v attached a diagram below so you can further understand it.   

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ssarfraz | Student, Professional | (Level 2) Honors

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Sublimation is the transition of a substance directly from the solid to the gas phase without passing through an intermediate liquid phase.

Sublimation is an endothermic phase transition that occurs at temperatures and pressures below a substance's triple point in its phase diagram.

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