1. PART A: Which statement best expresses the central idea of the text? A. Math plays a vital role in scientists’ search for alien life as it helps them determine where and when life might exist and communicate with it. B. Math is a language that everyone understands on Earth, and it is likely that math is the foundation of all alien languages as well. C. While some scientists rely on math to contact aliens, it plays a larger role in general space exploration by helping astronomers get to space. D. While searching for alien life with math is exciting, scientists should be focusing on

Explanation:

Solids are divided into two main categories, crystalline solids and amorphous solids, based on how the particles are arranged.

Crystalline solids, or crystals, are regarded as "true solids." Minerals are crystalline solids. Common table salt is one example of this kind of solid. In crystalline solids, the atoms, ions or molecules are arranged in an ordered and symmetrical pattern that is repeated over the entire crystal.

Crystalline solids also exhibit anisotropy. This means that properties such as refractive index (how much light bends when passing through the substance), conductivity (how well it conducts electricity) and tensile strength (the force required to break it apart) will vary depending on the direction from which a force is applied. Crystalline solids also exhibit cleavage; when broken apart, the pieces will have planed surfaces, or straight edges.

There are four types of crystalline solids: ionic solids, molecular solids, network covalent solids and metallic solids.

In amorphous solids (literally "solids without form"), the particles do not have a repeating lattice pattern. They are also called "pseudo solids." Examples of amorphous solids include glass, rubber, gels and most plastics. An amorphous solid does not have a definite melting point; instead, it melts gradually over a range of temperatures, because the bonds do not break all at once. This means an amorphous solid will melt into a soft, malleable state (think candle wax or molten glass) before turning completely into a liquid.

Amorphous solids have no characteristic symmetry, so they do not have regular planes of cleavage when cut; the edges may be curved. They are called isotropic because properties such as refractive index, conductivity and tensile strength are equal regardless of the direction in which a force is applied.