In Chemistry, there are three primary states of matter; solids, liquids, and gases. The states of matter are determined by the various properties of matter including; the types of atomic and molecular interactions, the amount of energy present in matter, and the average distance between particles.
With regards to atomic and molecular interactions, solids have the strongest intermolecular interactions, followed by liquids, and then gases. This is why solids are generally the densest state of matter, followed by liquids, and then gases.
With regards to the amount of energy present in matter, solids have the lowest amount of energy, followed by liquids, and then gases. This is why solids are generally the coldest state of matter, followed by liquids, and then gases.
Finally, with regards to the average distance between particles, solids have the shortest average distance between particles, followed by liquids, and then gases. This is why solids are generally the most compact state of matter, followed by liquids, and then gases.