Doing Solids: Crash Course Chemistry #33

Understanding Solids: Crystalline vs. Amorphous

The Perception of Chemicals

• Many people associate "chemicals" with negativity, thinking of them as dangerous or harmful substances, often linked to food and pollution.

• This perception typically overlooks the fact that most everyday materials, including solids like furniture and electronics, are also chemicals.

Characteristics of Solids

• Solids are diverse; they can be hard metals or soft materials like rubber and clay, each exhibiting unique properties based on their atomic structure.

• The characteristics of solids arise from the arrangement of electrons, chemical bonds, and intermolecular forces. There are two main classes: crystalline and amorphous solids.

Crystalline vs. Amorphous Solids

• Crystalline Solids: Atoms arranged in an orderly manner leading to predictable properties.

• Amorphous Solids: Lack a definite shape due to random atomic arrangements; examples include glass and certain biological tissues like fat.

Properties of Amorphous Solids

• Amorphous solids melt gradually rather than at a specific temperature due to the randomness in bond strength among particles. For instance, glass melts over a range rather than at a fixed point like ice does at 0°C.

• They respond differently to stress compared to crystalline solids; breaking along unpredictable lines leads to irregular shapes (e.g., broken glass). This characteristic is termed isotropy for amorphous solids versus anisotropy for crystalline ones.

Types of Crystalline Solids

• There are three types based on composition:

• Molecular Solids: Composed of covalent compounds with weak bonds (e.g., sugar).

• Ionic Solids: Formed from ionic compounds with high melting points (e.g., table salt).

Network Solids and Their Unique Properties

Overview of Network Solids

• Network solids are characterized by a rigid crystal structure formed by atoms, exemplified by diamonds which consist of carbon atoms arranged in a large crystalline formation.

• These structures can be conceptualized as giant molecules due to their extensive atomic arrangements.

Group 18 Solids: Noble Gases

• Noble gases, found in Group 18 of the periodic table, exhibit minimal interaction with each other, making it challenging to cool or pressurize them into liquid or solid states.

• When crystallization occurs, it is primarily due to weak Van der Waals forces, resulting in unstable structures that do not persist for long periods.

The Ubiquity and Structure of Metals

Characteristics of Metals

• Metals are prevalent in everyday life; they are present in devices we use and even within our bodies (e.g., dental work).

• The arrangement of metal atoms is orderly, forming various closest packing arrangements akin to efficiently stacking spheres (like ping pong balls).

Properties Resulting from Atomic Structure

• Metals exhibit malleability (ability to be shaped) and ductility (ability to be stretched into wires), stemming from the nature of their atomic bonds.

• The large size of metal atoms allows valence electrons to move freely, creating a "sea of electrons" that facilitates heat and electricity conduction.

Common Features Among Crystalline Solids

Characteristics Shared by Crystalline Structures

• All crystalline solids share common characteristics related to their uniform bond lengths and strengths; they require specific amounts of energy for breaking bonds.

• Compared to amorphous solids, crystalline solids tend to be more brittle and respond differently under force depending on the direction applied.

Conclusion on Solid Diversity