Using Materials

This section explains using materials covering corrosion and its prevention, the use of alloys, the use of ceramics, the use of polymers and provides a summary of materials and their uses.

Materials are essential to everyday life, and their properties determine their suitability for different applications. Understanding how materials behave and how they can be used effectively is crucial in chemistry. This section will cover corrosion and its prevention, the uses of alloys, ceramics, and polymers.

Corrosion and Its Prevention

Corrosion is a natural process that occurs when metals react with substances in their environment, particularly oxygen and water, leading to the deterioration of the metal. The most common example of corrosion is rusting, which specifically affects iron and its alloys, such as steel.

Rusting occurs when iron reacts with oxygen in the presence of water, forming hydrated iron(III) oxide (rust):

$$4Fe + 3O₂ + 6H₂O → 4Fe(OH)₃$$

Rusting weakens the metal, causing it to flake and become brittle.

Prevention of Corrosion

Several methods can be used to prevent or slow down the corrosion of metals:

Painting: Applying a layer of paint on the metal surface acts as a protective barrier, preventing oxygen and water from reaching the metal.

Galvanising: Involves coating the metal (usually iron or steel) with a layer of zinc. Zinc is more reactive than iron and corrodes first, protecting the underlying metal. If the zinc coating is damaged, the exposed zinc still offers protection by corroding before the iron.

Cathodic Protection: This method involves attaching a more reactive metal (such as magnesium) to the metal to be protected. The more reactive metal corrodes in place of the protected metal.

Alloying: Some metals are alloyed to make them more resistant to corrosion. For example, stainless steel is an alloy of iron, chromium, and nickel, which is highly resistant to rust.

Alloys as Useful Materials

Alloys are mixtures of a metal with other elements, typically other metals or non-metals. These mixtures are often more useful than pure metals because they possess improved properties, such as increased strength, resistance to corrosion, or improved hardness.

Common Alloys:

• Steel: Steel is an alloy of iron and carbon. It is much stronger than pure iron and can be further modified to suit specific applications, such as in construction, automotive industries, and tools.
• Stainless Steel: An alloy of iron, carbon, and chromium. It is resistant to rusting and corrosion, making it ideal for use in kitchen utensils, medical equipment, and structures exposed to moisture.
• Bronze: An alloy of copper and tin. It is used in making coins, sculptures, and musical instruments because it is durable and has a pleasing appearance.
• Brass: An alloy of copper and zinc. It is used for making items that need to resist corrosion, such as in plumbing fittings and electrical connectors.

Advantages of Alloys:

• Improved Strength: Many alloys are stronger than the pure metals from which they are made.
• Corrosion Resistance: Alloys like stainless steel are much more resistant to corrosion than iron or steel alone.
• Durability and Hardness: Alloys can be made to be harder and more durable, which is important in applications like tools and machinery.

Ceramics

Ceramics are non-metallic, inorganic materials made by heating substances such as clay, silica, and alumina to high temperatures. Once heated, ceramics harden and retain their shape. They are typically very strong, durable, and heat-resistant, making them useful in a variety of applications.

Common Ceramics:

• Porcelain: A fine, white ceramic made from kaolin clay and fired at a high temperature. It is used to make items like crockery, tiles, and electrical insulators.
• Bricks: Made from clay and fired in kilns, bricks are durable and strong, making them ideal for construction.
• Glass: Made from silica (sand) and other ingredients, glass is widely used in windows, containers, and optical fibres. It is transparent, hard, and can be made to have specific properties like resistance to heat or chemicals.
• Cement: A ceramic material used as a binding agent in construction. It is mixed with water to form a paste, which hardens and binds other materials, such as sand and gravel, to form concrete.

Properties of Ceramics:

• Hardness: Ceramics are typically hard and can withstand high pressure without breaking.
• Brittleness: While hard, ceramics are also brittle and can break or shatter if subjected to sudden impact or stress.
• Heat Resistance: Ceramics can withstand high temperatures, making them suitable for use in situations where materials are exposed to heat, such as in ovens or engines.

Polymers

Polymers are large molecules made up of repeating units called monomers. Polymers can be natural, like rubber and cotton, or synthetic, like plastics and nylon. They are extremely versatile materials and are used in a wide variety of applications due to their range of properties.

Types of Polymers:

• Thermoplastics: These are polymers that soften when heated and can be moulded into different shapes. They can be reused and recycled. Common examples include polyethylene (used in plastic bags), polystyrene (used in disposable cups), and PVC (used in pipes and electrical cables).
• Thermosetting Plastics: These polymers do not soften when heated. Once set, they are rigid and cannot be reshaped. They are used in applications that require materials with high resistance to heat and pressure, such as bakelite (used in electrical insulators) and epoxy resins (used in adhesives and coatings).
• Rubber: Natural rubber is made from the sap of rubber trees, while synthetic rubber is made from petroleum-based products. Rubber is elastic, making it ideal for use in tyres, footwear, and seals.

Properties of Polymers:

• Flexibility: Many polymers are flexible and can be moulded into various shapes, making them ideal for a wide range of products.
• Lightweight: Polymers are often lighter than metals and ceramics, making them suitable for applications where weight is a concern, such as in packaging and clothing.
• Durability: Some polymers, like nylon and Teflon, are extremely durable and resistant to wear and corrosion.

Uses of Polymers:

• Packaging: Plastics like polyethylene, polypropylene, and polystyrene are commonly used in packaging due to their lightweight, durability, and versatility.
• Clothing: Synthetic fibres like polyester and nylon are used to make clothing that is durable and resistant to stains and wrinkles.
• Medical Devices: Polymers are used in medical devices such as syringes, catheters, and drug delivery systems because they can be easily moulded into precise shapes.

Summary of Materials and Their Uses

Materials such as metals, alloys, ceramics, and polymers are essential to our modern world. Each material has unique properties that make it suited to specific applications, from the corrosion resistance of alloys to the heat resistance of ceramics and the flexibility of polymers. Understanding the properties of these materials and how they can be used or prevented from degrading (such as through corrosion) is essential in chemistry and helps improve the design of products and the sustainability of materials.