Problem 7 - Entrance Test

Let's analyze the properties: - **Sharp melting point**: Crystalline solids (true solids) have a sharp and characteristic melting point because all the constituent particles are arranged in a regular, ordered pattern, and thus, the forces of attraction between them are uniform. Amorphous solids, on the other hand, melt over a range of temperatures. - **Anisotropy**: Crystalline solids are anisotropic, meaning their physical properties (like electrical resistance, refractive index, thermal expansion) show different values when measured along different directions in the same crystal. This is due to the ordered arrangement of particles. - **Long-range order in constituent particles**: This is the defining characteristic of crystalline solids. Their constituent particles (atoms, ions, or molecules) are arranged in a regular, repeating pattern extending throughout the crystal. - **Isotropy**: This property means that physical properties are the same in all directions. Amorphous solids are isotropic, similar to liquids and gases, because their particles are arranged randomly and there is no long-range order. Crystalline solids are *not* isotropic; they are anisotropic. Therefore, Isotropy is not a characteristic of a true solid (crystalline solid).