One common characteristics of solids, liquids and gasses is that?
Answer Details
The correct answer is: their molecules are always in motion.
Solids, liquids and gases are the three main states of matter, and they all share the characteristic that their molecules are always in motion. However, the motion of the molecules varies between the three states. In solids, the molecules are packed tightly together and vibrate around fixed positions. In liquids, the molecules have more freedom of movement and can slide past each other. In gases, the molecules move freely and randomly in all directions.
None of the other options are correct. Solids and liquids have a fixed volume, but gases do not. The size of the molecules varies between the three states. The intermolecular forces also vary between the states; solids have the strongest intermolecular forces, followed by liquids and then gases.