Diagram 1 contains the state of matter that occurs after a solid melts.
Step-by-step explanation:
The diagram 1 represents the liquid state of matter. The liquid state of matter is represented by the balls that are loosely placed. This means there is ample amount of intermolecular spaces but not as much as like gases.
While the diagram 2 represents molecules of gases which has much more intermolecular spaces.
The diagram 3 represents solids where the molecules are very closely packed with minimal amount of intermolecular spaces.
Diagram 4 represents the ions of opposite charges with opposite charges being coloured in red and blue separately.
A solid melts into a liquid. So the liquid state of matter is represented in the diagram 1. Hence diagram 1 is the answer.