Amorphous and Crystalline Solids PDF

# Amorphous and Crystalline Solids ## Learning Competencies - Describe the structure of crystalline and amorphous solids. ## What are the Two General Types of Solids? - What features can be used to distinguish a crystalline solid from an amorphous solid? The differences in properties of these tw...

# Amorphous and Crystalline Solids ## Learning Competencies - Describe the structure of crystalline and amorphous solids. ## What are the Two General Types of Solids? - What features can be used to distinguish a crystalline solid from an amorphous solid? The differences in properties of these two groups of solids arise from the presence or absence of long-range order of arrangements of the particles in the solid. ## Arrangement of Particles The components of a solid can be arranged in two general ways: ### Crystalline Solid - They can form a regular repeating three-dimensional structure called a crystal lattice, thus producing a crystalline solid ### Amorphous Solid - They can aggregate with no particular long-range order, and form an amorphous solid (from the Greek *amorphos*, meaning "shapeless") ## Crystalline solids Crystalline solids are arranged in fixed geometric patterns or lattices. - Examples of crystalline solids are ice and sodium chloride (NaCl), copper sulfate (CuSO4), diamond, graphite, and sugar (C12H22O11). The ordered arrangement of their units maximizes the space they occupy and are essentially ## Examples - Diamonds - Table salt ## Crystalline Solids (vocabulary) ### Lattice - Is a three-dimensional system of points designating the positions of the components (atoms, ions, or molecules) that make up a crystal ### Unit cell - Is the smallest repeating unit of a lattice ## Common Unit Cells and Lattices - Cubic - Tetragonal - Rhombohedral - Orthorhombic - Monoclinic - Triclinic - Hexagonal ## Amorphous Solids Amorphous solids have a random orientation of particles. - Examples of amorphous solids are glass, plastic, coal, and rubber. They are considered super-cooled liquids where molecules are arranged in a random manner similar to the ## Examples - Glass - Rubber ## Differences between Amorphous and Crystalline Solids | | Amorphous Solids | Crystalline Solids | |---------------|--------------------------------------|-------------------------------------------------------| | Arrangement of | Particles are randomly arranged and | Particles (atoms, molecules or ions) are closely | | Particles | have no ordered structure. | packed and have an ordered three-dimensional | | | | structure. | | Melting Point | Do not have sharp melting points; | Sharp melting points | | | they melt over a wide range of | | | | temperatures | | | Examples | Glass, rubber, and plastics | Diamond, graphite, NaCl, CuSO4, graphite, NaCl, | | | | and MgSO4. | ## For More Information… More than 90% of **naturally occurring and artificially prepared solids are crystalline**. - Minerals, sand, clay, limestone, metals, alloys, carbon (diamond and graphite), salts (e.g. NaCl and MgSO4), all have crystalline structures. - They have structures formed by repeating three-dimensional patterns of atoms, ions, or molecules. - The repetition of structural units of the substance over long atomic distances is referred to as **long-range order**. - Amorphous solids (e.g. glass), like liquids, do not have long-range order, but may have a limited, localized order in their structures. ## Figure 1: Crystalline and amorphous quartz - Crystalline and amorphous quartz with a blue sky background. ## Behavior When Heated- Crystalline - The presence or absence of long-range order in the structure of solids results in a difference in the behavior of the solid when heated. - The structures of crystalline solids are built from repeating units called **crystal lattices**. The surroundings of particles in the structure are uniform, and the attractive forces experienced by the particles are of similar types and strength. ## Crystalline Vs. Amorphous Solids - Heat of Fusion & Melting Point ### Crystalline Solids - A diagram of a crystalline solid is shown with the following diagram: - A cube is shown with labeled “unit cells” in each section. - The caption below this diagram is "Crystalline Solid" - A smaller diagram of a unit cell is shown with the following labels: - "Unit cell" - "a" - "b" - "c" - "α" - “β” - “γ” - The caption below this diagram is "Parameters of Unit Cell" - “Length of edges= a, b, c” - “Angle between edges= α,β,γ” - Another diagram shows a cube, with the following labels: - A cube is shown with the following labels: - “solid” - “liquid” - “Δ” - The caption below this diagram is “Crystalline Solids” and lists the following: - “No fixed temperature” - “Absorbing fixed heat energy” - “Δ= Heating” - The caption below the diagrams reads: - "Properties of the unit cell = Properties of the crystalline solid" - The caption below that is “- Fixed temperature is the melting point. - “- Energy required for the change of state is the heat of fusion” - “*Crystalline solids have fixed heat of fusion & the melting point." ## Figure 2: Examples of crystalline solids - a) Pyrite (fool's gold) - b) Fluorite - c) Amethyst The images are of a gold-brown rock, a purple crystal, and a purple rock partially broken in half. ## Behavior When Heated- Amorphous - Amorphous solids soften gradually when they are heated. They tend to melt over a wide range of temperatures - This behavior is a result of the variation in the arrangement of particles in their structures, causing some parts of the solid to melt ahead of other parts. ## Crystalline Vs. Amorphous Solids - Heat of Fusion & Melting Point ### Amorphous Solids -A diagram of an amorphous solid is shown with the following diagram: - A container with the label "Amorphous solid" shows a collection of irregular shapes. - A container with the label "liquid" shows a collection of small, round shapes. - “Δ” is shown between the two containers - The caption below this diagram is “Amorphous Solids” and lists the following: - “Transformation seen over a range of temp & heat energy” - “Δ= Heating” - The caption below the diagrams reads: - "*Amorphous solids does not have fixed value for temperatore […]" ## Figure 3: Examples of amorphous solids - Charcoal - Rubber bands - Glass paper weights - Plastic lunch boxes The images of the following are shown: - a very dark gray pile of charcoal - a pile of orange twist ties - a glass fishbowl filled with clear, smooth rocks - a pile of white plastic lunch boxes.