___________ is the state of matter in which the constituent molecules are the most loosely packed.

1. Solid atoms are very tightly packed because atoms are very close to each other. So solids have a definite shape and size.
2. Liquids have the arrangement of the atoms looser than that of in solid. So, liquids do not have any definite shape but they have definite volume.
3. In gases, atoms are very loosely packed because of the high kinetic energy of atoms in the gas phase.
4. So, gas molecules experience very less force of attraction. As a result, gases do not have definite shape and volume.

Hence, gas is the state of matter in which the constituent molecules are the most loosely packed.