Identify common properties of the molecules in a compound with a liquid crystal phase:. a. contain ions
b. contain aromatic groups
c. contain polar groups
d. have long molecules

d. have long molecules

Explanation:

One class of substance tends so greatly toward an ordered arrangement that a melting crystal first forms a milky liquid, called the paracrystalline state, with characteristically crystalline properties. At higher temperatures, this milky fluid changes sharply into a clear liquid that behaves like an ordinary liquid. Such substances are known as liquid crystals.

Molecules that exhibit liquid crystallinity are usually long and rodlike. An important class of liquid crystals is called thermotropic liquid crystals, which form when the solid is heated.

The two common structures of thermotropic liquid crystals are nematic and smectic. In smectic liquid crystals, the long axes of the molecules are perpendicular to the plane of the layers. The layers are free to slide over one another so that the substance has the mechanical properties of a two-dimensional solid. Nematic liquid crystals are less ordered. Although the molecules in nematic liquid crystals are aligned with their long axes parallel to one another, they are not separated into layers.