Answer : The correct answer is, Sublimation and Melting process.
Explanation :
- Solid state : In this state, the molecules are closely and tightly packed. There is no vacant space present in it and there is strong inter-molecular force of attraction. The atoms are not free to move in this state.
- Liquid state : In this state, the molecules are loosely packed and there is an intermediate vacant space present in it and there is less inter-molecular force of attraction. The atoms are free to move in this state.
- Gas state : In this state, the molecules are very loosely packed and there is a lot of vacant space present in it and there is very less inter-molecular force of attraction. The atoms are easily free to move in this state.
So, there are two processes in which changes of state of atoms that cannot move past one another become free to move which are sublimation and melting process.
Sublimation : It is a process in which a solid directly changes to gaseous phase.
Melting : It is process in which a solid changes into liquid phase by providing heat.