Прочтите текст про себя (контрольное время чтения — 4 минуты). Molecules in Solids
Having their own shape is a characteristic feature of solids since they have their own shape rather than that of the container (as for liquids and gases) and generally do not flow, the extent of molecular motion in a solid is even more limited than that in a liquid. True solids are crystalline, bounded by plane surfaces that meet in a definite dihedral angle, and have a characteristic melting point. The molcculcs in a solid have the same temperature, and if they are molecules of the same
substancc, they arc moving at the same average velocity, the motion of molcculcs in a solid must be confined, and, probably, it is a vibration or oscillation about a fixed point.
Crystals composed of molecules may evaporate in a manner similar to that of liquids. This phenomenon is called sublimation, and it may.be noticed in solid carbon dioxide (dry ice), paradichlorobcnzcnc, camphor, and many odorous solids. Non-molccular solids show little tendency to sublime. The Van dcr Waals force between the particles in molecular solids is, apparently, less in general than the coulomb forces between ions in non-molccular solids. As with liquids, solids vaiy greatly in their tendency to sublime, and the rate of sublimation varies with the temperature and inversely with the pressure. In some solids the ciystal is composed of molecules in a pattern Uiat repeats.
