Question

The process by which a solid changes directly into gas is called:
(A) Decantation
(B) Sublimation
(C) Condensation
(D) Sedimentation

Answer 1

Hint: The conversion of carbon dioxide gas from dry ice is also an example of this reaction. In this process, there is no requirement of a solvent. A solid directly gets converted to gas.

Complete step by step answer:
We need to give the name of the process in which a solid directly gets converted to its gaseous form. So, here the conversion of solid state to liquid state does not occur.
- The process in which a solid directly gets converted directly to a gaseous state is called sublimation. So, here solid state does not get converted to liquid state in the process of attaining gaseous form.
- An example of a sublimation process is dry ice. We know that dry ice is solid carbon dioxide. So, when we keep dry ice at room temperature, it gives gaseous carbon dioxide which is a result of sublimation reaction. This reaction can be give as
     \[C{O_{2(s)}}\xrightarrow{{{\text{Sublimation}}}}C{O_{2(g)}}\]

- Decantation is a process in which we take the clear liquid out from the mixture when solid is settled at the bottom.
- Condensation is a process in which a gas is converted to its liquid form.
- Sedimentation is a process in which solids that are not soluble in the liquid get collected at the bottom of the vessel due to gravity.
So, the correct answer is “Option B”.

Note: Remember that the process of conversion of solid state to liquid state is called melting. Conversion of a liquid state of a compound to its gaseous state is called evaporation.