core 4 - p3 Flashcards
(25 cards)
What are the three primary types of atomic bonding?
Covalent, ionic, and metallic bonding
Define element and compound with examples.
-Element: Pure substance of one type of atom (e.g., oxygen, O₂).
-Compound: Substance formed by chemically bonded elements (e.g., water, H₂O).
What distinguishes crystalline solids from amorphous solids?
-Crystalline: Ordered atomic structure (e.g., diamond).
-Amorphous: Disordered atomic structure (e.g., glass).
What is metallic bonding? How does it explain properties like conductivity?
Metallic bonding involves a “sea of electrons” shared among metal ions. Free electrons enable conductivity and malleability.
What is a polymer? Name two types based on structure.
A polymer is a large molecule made of repeating monomers. Types:
-Linear (e.g., polyethylene).
-Cross-linked (e.g., vulcanized rubber).
What are van der Waals forces? Why are they important in polymers?
Weak intermolecular forces between molecules. They hold polymer chains together, affecting flexibility and melting points.
Define composite material and provide an example.
A composite combines two or more materials for enhanced properties (e.g., fiberglass: glass fibers + polymer resin).
What is concrete composed of, and why is it a composite?
Aggregate (sand/gravel) + cement + water. The cement binds the aggregate, creating a stronger material than its components.
What are fiber-reinforced polymers (FRPs)? Give two examples.
Composites with fibers (e.g., carbon, glass) in a polymer matrix. Examples:
-CFRP (carbon fiber).
-GFRP (glass fiber).
What is the purpose of sintering in material processing?
To fuse powdered materials using heat/pressure without melting, enhancing strength and density (e.g., ceramic tiles).
What is Young’s modulus? Provide its formula.
Measures stiffness. Formula: E = Stress / Strain= (F / A) / (ΔL / L0)
Define stress and strain with equations.
Stress (σ): Force per unit area ( σ = F/A ).
Strain (ε): Deformation per original length ( ε = ΔL / L0 ).
What does a stress-strain curve reveal about a material?
Elastic region, yield point, plastic deformation, ultimate tensile strength, and fracture point.
How does Hooke’s Law relate to the elastic region of a stress-strain curve?
Stress is proportional to strain within the elastic limit ( σ=Eε ).
What is fatigue testing (e.g., Wohler test)?
Determines a material’s resistance to cyclic loading, simulating real-world stress conditions (e.g., bridges, aircraft).
What is the salt spray test used for?
Evaluates corrosion resistance by exposing materials to a saline mist (simulates marine environments).
How does the Taber abrasion test measure wear resistance?
How does the Taber abrasion test measure wear resistance?
What is permeability in materials?
Ability to allow magnetic flux to pass through (e.g., iron has high permeability; wood has low).
What is hardenability? How does it differ from hardness?
Hardenability is the depth to which a material can be hardened by heat treatment. Hardness measures surface resistance to indentation.
Name three injection moulding materials and their uses.
-ABS: Automotive parts, toys.
-Polycarbonate (PC): Bulletproof glass, eyewear.
-Polyethylene (PE): Packaging, containers.
What are thermoset polymers? Give an example.
Polymers that irreversibly harden when cured (e.g., epoxy, Bakelite).
What is the glass transition temperature (Tg ) in polymers?
The temperature at which a polymer transitions from rigid to rubbery (e.g., PMMA softens at ~105°C).
What is roll forming in metal processing?
A continuous bending process using rollers to shape metal sheets into profiles (e.g., gutters, rails).
Define powder coating and its advantages.
A dry finishing process where electrostatically charged powder is applied to surfaces. Advantages: Durability, corrosion resistance, eco-friendly.
