Answer:
Step-by-step explanation:
There are three states of matter; solid, liquid and gases.
The particles in solids are highly compact and are close to each other. These particles do not really move (there movement is insignificant) hence the reason for there defined shape. However when these solids are melted into liquid, its particles move freely in its liquid form and hence they do not have a defined shape (they assume the shape of any container they are put in).
For example, the particles in an an ice bar (solid) have restricted movement but will move freely when melted into water (liquid).