TOPIC FOUR: USING MATERIALS

In chemistry, classifying materials is essential because it helps us understand their properties and how they are used in everyday life. Materials are typically classified into different categories based on their origin, structure, and properties.

A. Based on Origin:

• Natural Materials:

  • Definition: Materials that are obtained directly from nature, without significant alteration.

  • Examples: Wood, cotton, wool, silk, metals (iron, copper), rubber, stone.

  • Uses:

    • Wood is used in furniture and construction.

    • Wool and cotton are used for making fabrics and clothing.

    • Iron and copper are used in construction and electrical wiring.

• Synthetic (Man-made) Materials:

  • Definition: Materials that are artificially produced, typically in laboratories or factories through chemical processes.

  • Examples: Plastics (polyethylene, PVC), nylon, polyester, synthetic rubber, composite materials (fiberglass).

  • Uses:

    • Plastics are used in packaging, bottles, and household products.

    • Nylon and polyester are used for clothing and fabrics.

    • Synthetic rubber is used in tires and hoses.

B. Based on Structure:

• Elements:

  • Definition: Pure substances consisting of only one type of atom.

  • Examples: Iron (Fe), Copper (Cu), Oxygen (O₂), Carbon (C).

  • Uses:

    • Iron is used in construction.

    • Oxygen is used in respiration and industrial processes.

    • Carbon in the form of graphite is used in pencils, while diamond is used in jewelry and cutting tools.

• Compounds:

  • Definition: Substances composed of two or more elements chemically combined in fixed proportions.

  • Examples: Water (H₂O), Sodium Chloride (NaCl), Carbon Dioxide (CO₂).

  • Uses:

    • Water is essential for life and is used in cleaning, drinking, and cooking.

    • Sodium chloride (table salt) is used in food preparation.

    • Carbon dioxide is used in the production of carbonated drinks and fire extinguishers.

• Mixtures:

  • Definition: Substances made of two or more elements or compounds that are physically combined and can be separated by physical means.

  • Examples: Air (a mixture of gases), alloys (mixture of metals), sea water (water and dissolved salts).

  • Uses:

    • Air is necessary for breathing.

    • Alloys like steel are used in construction and manufacturing.

    • Sea water provides salt and is a habitat for marine life.

C. Based on Properties:

• Metals:

  • Definition: Materials that are typically hard, shiny, malleable, ductile, and good conductors of heat and electricity.

  • Examples: Iron, copper, aluminum, gold.

  • Uses:

    • Iron is used in construction.

    • Copper is used in electrical wiring.

    • Aluminum is used in cans, foil, and aircraft.

• Non-metals:

  • Definition: Materials that are usually not shiny, brittle, and poor conductors of heat and electricity.

  • Examples: Carbon, sulfur, nitrogen, oxygen.

  • Uses:

    • Carbon is used in pencils (graphite) and fuel (coal).

    • Oxygen is essential for respiration and combustion.

• Polymers:

  • Definition: Large molecules made up of repeating smaller units (monomers). Can be natural or synthetic.

  • Examples: Plastic (synthetic polymer), rubber (natural polymer), nylon (synthetic polymer).

  • Uses:

    • Plastics are used in packaging, household items, and electronics.

    • Rubber is used in tires and erasers.

Importance of Classifying Materials:

• Understanding Properties: Classification helps in identifying the specific properties of materials, such as strength, conductivity, or flexibility. This understanding guides how materials can be used in different applications.

• Choosing the Right Material for Use: Knowing whether a material is natural or synthetic, or whether it is a metal or a non-metal, helps in selecting the best material for a given purpose. For example, choosing metals for electrical wires due to their conductivity.

• Environmental Impact: Classifying materials based on their origin (natural or synthetic) helps in understanding their environmental impact. Natural materials are often biodegradable, while synthetic materials, like plastics, may not be. This knowledge helps in making environmentally responsible decisions, such as choosing recyclable materials.

• Improving Efficiency: Classification helps industries and manufacturers select materials that optimize performance. For example, selecting heat-resistant materials like stainless steel for kitchen appliances ensures durability and efficiency.

• Recycling and Sustainability: Materials are classified to determine whether they can be recycled or reused. Recycling metal, glass, and certain plastics reduces environmental waste and conserves resources.

POLYMERS

 The word polymer comes from two Greek words `poly` meaning many and `mer` meaning molecules. Thus polymers are; lager molecules formed by combining many small molecules. 

 Polymers form non metallic materials like plastics and fibers. Therefore; they are important as materials in making many objects used in daily life 

Examples of polymers used as materials and the objects in daily life they form 

Classification of Materials (Natural and Synthetic)

Polymers are large molecules composed of repeating subunits known as monomers. They can be either natural or synthetic and are widely used in various everyday objects due to their versatile properties. Here are some examples of polymers and the materials or objects they form in daily life:

1. Polyethylene (PE)

• Type: Synthetic Polymer

• Objects Formed:

  • Plastic Bags: Used for grocery shopping and packaging.

  • Plastic Bottles: Commonly used for detergents and personal care products.

  • Food Packaging: Used for cling films and containers.

2. Polypropylene (PP)

• Type: Synthetic Polymer

• Objects Formed:

  • Plastic Containers: Used for food storage, lunch boxes, and packaging.

  • Car Bumpers: Used in automobiles due to its impact resistance.

  • Ropes and Fibers: Used for making durable ropes, carpets, and textiles.

3. Polyvinyl Chloride (PVC)

• Type: Synthetic Polymer

• Objects Formed:

  • Pipes: Used for plumbing and drainage systems.

  • Vinyl Flooring: Used in homes, schools, and offices.

  • Electrical Cable Insulation: Used to insulate wires and cables due to its electrical insulation properties.

4. Polystyrene (PS)

• Type: Synthetic Polymer

• Objects Formed:

  • Disposable Cups and Plates: Used in food packaging and as disposable dinnerware.

  • Styrofoam: Used for insulation, packaging materials, and disposable coffee cups.

  • Model Kits and Toys: Used for creating lightweight plastic parts.

5. Polyethylene Terephthalate (PET)

• Type: Synthetic Polymer

• Objects Formed:

  • Water and Soda Bottles: Widely used for packaging beverages.

  • Food Containers: Used for take-out and storage of food.

  • Synthetic Fibers (Polyester): Used in fabrics for clothing, bedding, and upholstery.

6. Nylon (Polyamide)

• Type: Synthetic Polymer

• Objects Formed:

  • Clothing (Stockings, Sportswear): Known for its strength, elasticity, and resistance to wear.

  • Ropes and Fishing Nets: Used for making durable, strong ropes and nets.

  • Mechanical Parts (Gears, Bearings): Used in mechanical applications for its wear resistance and durability.

7. Rubber (Natural and Synthetic Rubber)

• Type: Natural and Synthetic Polymer

• Objects Formed:

  • Tires: Used in vehicles due to its elasticity, durability, and grip.

  • Rubber Bands: Used for holding things together.

  • Shoe Soles: Used in footwear for flexibility and durability.

8. Polytetrafluoroethylene (PTFE - Teflon)

• Type: Synthetic Polymer

• Objects Formed:

  • Non-stick Cookware: Used in pots, pans, and kitchen utensils for its non-stick properties.

  • Electrical Insulation: Used in high-performance insulation for cables and wiring.

  • Water-repellent Fabrics: Used in raincoats and outdoor gear.

9. Polycarbonate (PC)

• Type: Synthetic Polymer

• Objects Formed:

  • Eyeglass Lenses: Used in glasses and sunglasses due to its clarity and shatter resistance.

  • Compact Discs (CDs, DVDs): Used for making optical discs.

  • Greenhouse Panels: Used in construction due to its strength and transparency.

10. Cellulose (Natural Polymer)

• Type: Natural Polymer

• Objects Formed:

  • Paper and Cardboard: Used for books, writing paper, and packaging.

  • Cotton Fabrics: Used for clothing, bed sheets, and towels.

  • Wood Products: Used in construction, furniture, and tools.

11. Polyurethane (PU)

• Type: Synthetic Polymer

• Objects Formed:

  • Foam Cushions: Used in furniture, mattresses, and car seats for comfort and support.

  • Shoe Soles: Used for making lightweight and durable footwear.

  • Insulation Panels: Used in building construction for thermal insulation.

12. Silicone (Siloxane Polymer)

• Type: Synthetic Polymer

• Objects Formed:

  • Bakeware: Used for flexible, heat-resistant baking molds.

  • Medical Implants: Used in various medical applications such as prosthetics.

  • Sealants and Adhesives: Used for sealing gaps in windows, bathrooms, and electronics.

13. Acrylic (Poly(methyl methacrylate) - PMMA)

• Type: Synthetic Polymer

• Objects Formed:

  • Acrylic Sheets (Plexiglass): Used as a lightweight and shatter-resistant alternative to glass in windows, aquariums, and displays.

  • Paints: Used in water-based acrylic paints.

  • Lighting Fixtures: Used for transparent or colored light covers.

14. Bakelite

• Type: Synthetic Polymer (Thermosetting Plastic)

• Objects Formed:

  • Electrical Switches and Sockets: Used due to its electrical insulating properties.

  • Radio and Telephone Casings: Used for early models of radios and telephones.

  • Cookware Handles: Used for heat-resistant handles on kitchen pots and pans.

15. Kevlar (Aramid Polymer)

• Type: Synthetic Polymer

• Objects Formed:

  • Bulletproof Vests: Used in protective clothing for law enforcement and military.

  • High-strength Cables: Used in bridges and construction.

  • Sports Equipment: Used in helmets and body armor due to its high strength and lightweight properties

Plastics and fibers can each be classified into natural and artificial

1. Plastics

A. Natural Plastics:

• Definition: Natural plastics are derived from natural materials such as plants or animals and are used with little to no modification.

• Examples:

  • Natural Rubber: Derived from the latex of rubber trees (Hevea brasiliensis). It is used in products such as tires, gloves, and erasers.

  • Celluloid: Derived from cellulose from plant sources, primarily wood pulp. It was historically used in photographic films and decorative items.

  • Shellac: A resin secreted by the female lac bug, used as a natural plastic in coatings, varnishes, and sealants.

B. Artificial (Synthetic) Plastics:

• Definition: Synthetic plastics are man-made materials created from petrochemicals or other chemical processes.

• Examples:

  • Polyethylene (PE): Used in plastic bags, packaging materials, and bottles.

  • Polyvinyl Chloride (PVC): Used in pipes, electrical insulation, and vinyl flooring.

  • Polystyrene (PS): Used in disposable cups, plates, and insulation materials (Styrofoam).

  • Polyethylene Terephthalate (PET): Used in plastic bottles and food containers.

2. Fibers

A. Natural Fibers:

• Definition: Natural fibers are obtained from plants, animals, or minerals and can be spun into threads or ropes.

• Examples:

  • Cotton: A plant fiber obtained from the cotton plant. It is widely used in making clothing, towels, and bed sheets.

  • Wool: An animal fiber obtained from the fleece of sheep. It is used in making warm clothing such as sweaters, blankets, and carpets.

  • Silk: An animal fiber obtained from the silkworm cocoon. It is used in luxury clothing, scarves, and upholstery.

  • Linen: A plant fiber obtained from the flax plant. It is used in making clothing, tablecloths, and handkerchiefs.

B. Artificial (Synthetic) Fibers:

• Definition: Synthetic fibers are man-made fibers created through chemical processes, often derived from petrochemicals.

• Examples:

  • Nylon: A synthetic fiber used in making ropes, stockings, tents, and parachutes.

  • Polyester: A synthetic fiber used in clothing, upholstery, and packaging materials.

  • Acrylic: A synthetic fiber used in making sweaters, blankets, and outdoor fabrics.

  • Rayon: A semi-synthetic fiber made from cellulose (natural polymer), but chemically treated to create a versatile fiber used in clothing and textiles

Plastics can further be classified into; Thermosetting plastics and thermo-softening plastics (thermoplastics) 

Thermosetting plastics harden on heating and when they are over heated, they burn or decompose. Thermo-softening plastics soften on heating and can be molded and remolded into new shapes.

1. Thermosetting Plastics (Thermosets)

Definition:

Thermosetting plastics are plastics that, once heated and molded into shape, cannot be melted or reshaped again. When exposed to heat, they undergo a chemical reaction that hardens them permanently.

Properties:

• Hard and Rigid: Once set, they become tough and inflexible.

• Resistant to Heat: They do not melt when reheated; instead, they may burn or decompose.

• Durable: Typically strong and resistant to wear, making them ideal for high-temperature applications.

• Non-recyclable: Since they cannot be remelted, they cannot be recycled by melting and reshaping.

Examples and Uses:

• Bakelite:

  • Used for: Electrical switches, plugs, and sockets due to its excellent insulating properties and heat resistance.

• Melamine:

  • Used for: Kitchenware such as plates, cups, and countertops.

• Epoxy Resins:

  • Used for: Adhesives, coatings, and electronics due to its strong bonding capabilities.

• Polyurethane (when used as a thermoset):

  • Used for: Insulation panels, foam seating, and protective coatings.

• Urea-Formaldehyde:

  • Used for: Electrical fittings and adhesives, especially in wood products.

2. Thermo-softening Plastics (Thermoplastics)

Definition:

Thermo-softening plastics (or thermoplastics) are plastics that can be repeatedly melted and reshaped when heated. These plastics become soft and malleable when heated and harden again upon cooling.

Properties:

• Softens when Heated: Can be remolded and reshaped multiple times.

• Recyclable: Since they can be melted and reshaped, thermoplastics are recyclable.

• Flexible or Rigid: They can be produced in a range of flexibility depending on the chemical composition.

• Less Heat Resistant: They tend to melt or deform when exposed to high heat.

Examples and Uses:

• Polyethylene (PE):

Used for: Plastic bags, bottles, and packaging materials.

• Polypropylene (PP):

Used for: Food containers, plastic chairs, car parts, and medical devices.

• Polyvinyl Chloride (PVC):

Used for: Pipes, cable insulation, and flooring.

• Polystyrene (PS):

Used for: Disposable cups, plates, and packaging (e.g., Styrofoam).

• Polyethylene Terephthalate (PET):

Used for: Beverage bottles and food packaging.

• Acrylic (PMMA):

Used for: Transparent glass substitutes (e.g., Plexiglass) and display cases.

• Nylon:

 Used for: Ropes, fabrics, and mechanical components such as gears.