Notes on Solids in Chemistry

Introduction

Common misconceptions about chemicals:
- People often think "chemicals = bad" or "chemicals = dangerous".
- Examples of phrases:
  - "I don’t give my kids food with chemicals."
  - "That factory puts chemicals in the water."
People tend to overlook solids as chemicals, thinking of them as "just stuff".
Almost everything we interact with daily is made of chemicals, primarily in solid form.

Solids are diverse beyond being just hard or strong.
Examples of solids:
- Metals: moldable under certain conditions.
- Rocks: lack of flexibility, can shatter.
- Softer solids: rubber, clay, styrofoam - behave differently due to their structure.

Key factors influencing solid characteristics:
- Arrangement of electrons
- Chemical bonds
- Intermolecular forces

Crystalline Solids
- Atoms/molecules arranged in a predictable manner.
- Break along defined planes.
- Anisotropic: properties vary based on direction.
Amorphous Solids
- Random arrangement of atoms/molecules.
- Lack sharp melting points; melt over a range of temperatures.
- Isotropic: respond to stress uniformly in all directions.
- Examples: foams, gels, glass, coal.
- Misconception: Glass is not a liquid.

Bond Strength: Random bond strengths due to random arrangement.
Melting Behavior:
- Melts gradually as weaker bonds break first.
- Contrast with crystalline solids that have specific melting points.
Breakage:
- Difficult to predict where breakage occurs due to random atomic structure.
- Resulting shapes are non-uniform (e.g., broken glass, coal).

Molecular Solids
- Made of covalent compounds.
- Examples: Ice, dry ice, sugar.
- Soft with low melting points due to weak van der Waals forces.
Ionic Solids
- Made of ionic compounds (e.g., sodium chloride).
- High melting points; soluble in water.
Atomic Solids
- Composed of individual atoms.
- Three subtypes:
  - Network Solids: rigid structure, e.g., diamonds.
  - Group 18 Solids: rare, due to weak bonding.
  - Metals: orderly arrangement; conductive due to mobile electrons.

Atoms arrange in closest packing arrangements.
Metals are malleable (can be shaped) and ductile (can be stretched).
Valence electrons are not held tightly, leading to a free-moving electron cloud, allowing conductivity.

Crystalline solids have uniform bonds, specific melting points, and are generally more brittle.
Amorphous solids exhibit diverse behaviors and properties based on random atomic arrangements.

All solids are a diverse array of chemicals.
Understanding the differences between amorphous and crystalline solids enhances comprehension of materials around us.
Properties of solids largely depend on the bonds between particles rather than the identity of the particles.