What property distinguishes liquids and gases from solids in terms of shape?
Liquids and gases are fluids that can flow and take the shape of their container due to their inability to maintain a fixed shape, unlike solids, which have a definite shape due to strong intermolecular forces resisting deformation.
Ref: NCBI Bookshelf, Ideal Gas Law: P1V1/T1 = P2V2/T2.