how does sublimation and deposition happen? Why don't they pass by the liquid phase?

Question

Usually, it's solid to liquid to gas and vice versa. How come some substances sublime without passing through the liquid phase? please connect it the intermolecular forces and kinetic energy. Ty!

Answer 1

Remember phase diagrams? They are plots of the state of matter at different temperatures and pressures. The pressure is the y axis, and the temperature is the x axis. If you draw a line parallel to the x axis (constant P) then you will have a situation in which you are heating up a sample, and you can observe what state the sample will undergo as it moves through different temperatures.

Lets look at CO2 and H2O at 1 atm:

ref: http://www.science.uwaterloo.ca/~cchieh/cact/c123/phasesdgm.html

You will see as you heat the sample up at 1 atm the H2O goes from solid to liquid and then to gas. That is just the nature of the matter at this pressure. If you lowered the Pressure below the triple point pressure (4.58 torr) the water would sublime; it would go directly from solid to gas with no liquid phase.

With CO2 at 1 atm you see that the condition is similar to water below it's triple point (CO2's triple point is at 5.11 atm) so CO2 will sublime directly to gas with no liquid phase.

Answer 2

Sublimation of an element or compound is the change from a solid directly to a gas with no intermediate liquid stage. Sublimation is a phase transition that occurs at temperatures and pressures below the triple point (see phase diagram).

At normal pressures, most chemical compounds and elements possess three different states at different temperatures. In these cases the transition from the solid to the gaseous state requires an intermediate liquid state. However, for some elements or substances at some pressures the material may transition directly from solid to the gaseous state. Note that the pressure referred to here is the vapor pressure of the substance, not the total pressure of the entire system.

The opposite of sublimation is deposition. The formation of frost is an example of meteorological deposition.

Answer 3

when a substantial amount of heat is either added or removed very fast from a system, then sublimation and deposition occurs (sublimation for added and deposition for removed). when this much heat is added, the substance heats up too quickly and immediately skips the liquid phase. hope that helps

Answer 4

Because something adds enough energy to the system to allow the solid to vapourise. Or, conditions do not exist to allow the liquid phase of the substance to exist.

To the best of my knowledge, it has nothing to do with kinetic energy.