What is the name of the process of a gas directly converted to solid?

Explanation:

The process by which gas I directly converted to solid is called deposition (reverse sublimation)

Deposition

Explanation:

Is the phase transition in which gas transforms into solid without passing through the liquid phase.

answer : a model is often used to explain and make things easier to understand when any scientific topic needs to be demonstrated and explained.

as in this case where a scientist wants to use a model to present the results of his detailed scientific investigation. he should do it as it will him to make the audience understand the concept in a much better way. also, it can be changed according to new scientific understandings.