Unlock the secrets of acing your chemistry exam with this comprehensive guide on chapter 9 of the CAIE syllabus -Metals. Dive into the world of metal science as we unravel the intricate details of their physical and chemical characteristics. This syllabus-specific guide, tailored for IGCSE Chemistry Revision, promises to equip you with the knowledge needed to excel in your exam preparation. From understanding the thermal and electrical conductivity of metals to exploring their applications in aircraft manufacturing, electrical wiring, and beyond, this guide is your key to mastering the essentials.

Prepare to unlock a deeper comprehension of the fascinating realm of metals and their diverse functionalities.

Properties of Metals 

Properties of Metals and General Chemical Properties:

General Physical Properties:

• Thermal Conductivity:

Metals generally have high thermal conductivity, meaning they efficiently conduct heat.

• Electrical Conductivity:

Metals are good conductors of electricity due to the presence of free electrons that can move easily through the metal lattice.

• Malleability and Ductility:

Metals are malleable (can be hammered into thin sheets) and ductile (can be drawn into wires) due to the ability of metal atoms to slide past each other without breaking bonds.

• Melting Points and Boiling Points:

Metals usually have high melting and boiling points. This is attributed to strong metallic bonds between positively charged metal ions and delocalized electrons.

General Chemical Properties of Metals:

•  Reactions with Dilute Acids:

Most metals react with dilute acids to produce salts and hydrogen gas. 

For example: Zn+2HCl→ZnCl₂+H₂

• Reactions with Cold Water and Steam:

Metals react with cold water to produce metal hydroxides and hydrogen gas. Some reactive metals can react with steam to form metal oxides and hydrogen gas. 

For example: 2Na+2H₂O→2NaOH+H₂

• Reactions with Oxygen:

Metals generally react with oxygen to form metal oxides. This reaction is often referred to as oxidation. 

For example: 4Fe+3O₂→2Fe₂O₃

Metals exhibit high thermal and electrical conductivity, malleability, ductility, and high melting/boiling points. They react with dilute acids, water, and oxygen to form various compounds.

Uses Of Metals 

Aluminium in Aircraft Manufacturing:

Reason:

Aluminium is used in the manufacture of aircraft due to its low density. The low weight of aluminium contributes to the overall lightness of the aircraft, which is crucial for fuel efficiency and manoeuvrability.

Aluminium in Overhead Electrical Cables:

Reasons:

1. Low Density: Aluminium’s low density makes it suitable for overhead electrical cables, reducing the weight of the cables and supporting structures.
2. Good Electrical Conductivity: Aluminium also possesses good electrical conductivity, allowing efficient transmission of electrical power over long distances.

Aluminium in Food Containers:

Reason:

Aluminium is used in food containers because of its resistance to corrosion. This property ensures that the metal does not react with the food, preserving its quality and safety.

Copper in Electrical Wiring:

Reasons:

1. Good Electrical Conductivity: Copper is an excellent conductor of electricity, making it ideal for use in electrical wiring and circuits.
2. Ductility: Copper is ductile, meaning it can be drawn into thin wires without breaking. This property facilitates the production of fine wires for various electrical applications.

In summary, the uses of metals are often tailored to their specific physical properties. Aluminium’s low density finds application in aircraft and overhead electrical cables, while its corrosion resistance makes it suitable for food containers. Copper’s combination of good electrical conductivity and ductility makes it indispensable for electrical wiring.

Alloys And Their Properties 

1. Definition of Alloys:

An alloy is a mixture of a metal with one or more other elements, often other metals or nonmetals. This combination enhances or modifies the properties of the base metal.

• Example – Brass:
  • Composition: Brass is an alloy composed of copper and zinc.
  • Properties: Brass exhibits a combination of properties from both copper and zinc, including improved hardness and corrosion resistance.
• Example – Stainless Steel:
  • Composition: Stainless steel is an alloy primarily composed of iron, chromium, nickel, and carbon.
  • Properties: Stainless steel is known for its corrosion resistance, hardness, and durability, making it suitable for various applications.

2. Properties of Alloys:

Alloys can be harder and stronger than pure metals due to the presence of different elements in their structure. The combination of metals and other elements often leads to improved mechanical properties compared to the individual components.

3. Uses of Alloys:

• Stainless Steel in Cutlery:
  • Properties Utilised: Stainless steel is preferred in cutlery due to its hardness and resistance to rusting. These properties ensure the durability and hygiene of cutlery items.

4. Identification of Alloys from Structure Diagrams:

Structural diagrams of alloys often represent a mixture of different-sized atoms, reflecting the presence of multiple elements in the alloy. The arrangement of these atoms influences the properties of the alloy.

In summary, alloys are mixtures of metals with other elements, offering improved properties compared to pure metals. Examples like brass and stainless steel showcase the versatility of alloys, and their use in applications like cutlery demonstrates how their unique physical properties make them valuable in various industries.

1. Reactivity Series Order:

Most Reactive

• Potassium, 
• Sodium, 
• Calcium, 
• Magnesium, 
• Aluminium, 
• Carbon, 
• Zinc, 
• Iron, 
• Hydrogen, 
• Copper, 
• Silver, 
• Gold.

Least Reactive

1. Reactions with Various Substances:
   1. Reactions with Cold Water:

Potassium, sodium, and calcium react with cold water.

2. Reaction of Magnesium with Steam:

Magnesium reacts with steam.

3. Reactions with Dilute Hydrochloric Acid:

• React: Magnesium, Zinc, Iron
• No reaction: Copper, Silver, Gold

2. Explanation in Terms of Reactivity Series:
   1. Position in Reactivity Series:

• Metals higher in the reactivity series (potassium, sodium, calcium) react with cold water, producing metal hydroxide and hydrogen gas.
• Magnesium, which is below calcium, reacts with steam.
• Metals below hydrogen (copper, silver, gold) do not react with dilute hydrochloric acid, as hydrogen ions are less likely to be displaced by these less reactive metals.

1. Deducing Reactivity from Experimental Results:

By observing reactions with water and acids, one can deduce the relative reactivity of metals. Metals higher in the reactivity series displace hydrogen more readily and react with a wider range of substances. Conversely, less reactive metals may only react under specific conditions or not at all with certain substances. The order of reactivity can be inferred based on the observed reactions.

Corrosion Of Metals

1. Conditions for Rusting of Iron and Steel:

Rusting of iron and steel occurs when both oxygen and water are present. The presence of these two elements, along with the iron or steel, leads to the formation of hydrated iron(III) oxide, commonly known as rust.

2. Common Barrier Methods:
   1. Painting: Applying a layer of paint creates a protective barrier between the metal surface and the surrounding environment.
   2. Greasing: Coating the metal with grease or oil forms a barrier that prevents contact with moisture and oxygen.
   3. Coating with Plastic: Placing a plastic coating over the metal surface acts as a barrier, isolating the metal from the external environment.
3. How Barrier Methods Prevent Rusting:
4. Excluding Oxygen or Water:
   1. Painting: The painted layer prevents direct contact between the metal surface and atmospheric oxygen, inhibiting the rusting process.
   2. Greasing: Grease or oil creates a hydrophobic barrier, repelling water and preventing it from reaching the metal surface. Additionally, it hinders the contact of oxygen with the metal.
   3. Coating with Plastic: A plastic coating forms a physical barrier that isolates the metal from both oxygen and water, preventing the conditions necessary for rusting.

In summary, barrier methods such as painting, greasing, and coating with plastic create a protective layer that excludes either oxygen, water, or both, thus preventing the conditions required for the rusting of iron and steel.

GCSE Chemistry – What is Corrosion and How to Stop it  #71

Extractions Of Metals 

1. Ease of Obtaining Metals and Reactivity Series:

• The ease of obtaining metals from their ores is related to their position in the reactivity series.
• Highly Reactive Metals: Metals high in the reactivity series, such as potassium and sodium, are obtained through electrolysis of their molten salts because they are too reactive to be extracted using carbon.
• Moderately Reactive Metals: Metals like iron and zinc, located mid-range in the reactivity series, are often extracted using carbon (coke) in a process called smelting.
• Less Reactive Metals: Less reactive metals, such as copper and silver, can often be obtained directly from their ores by methods like heating or reduction with carbon without the need for extensive processing.

2. Extraction of Iron from Hematite in the Blast Furnace:

• Burning of Carbon (Coke): Coke is burned to provide heat and produce carbon dioxide.
• Reduction of Carbon Dioxide to Carbon Monoxide: Carbon dioxide produced in the burning of coke is reduced to carbon monoxide.
• Reduction of Iron(III) Oxide by Carbon Monoxide: Carbon monoxide, a reducing agent, reduces iron(III) oxide to iron, producing carbon dioxide.
• Thermal Decomposition of Calcium Carbonate/Limestone: Limestone is thermally decomposed to produce calcium oxide, which reacts with impurities to form slag.
• Formation of Slag: Calcium oxide reacts with impurities to form slag, which floats on the molten iron and is removed.

3. Main Ore of Aluminium and Extraction by Electrolysis:

• Main Ore of Aluminium: Bauxite is the main ore of aluminium.
• Extraction Method: Aluminium is extracted from bauxite through electrolysis. The process involves the electrolysis of molten aluminium oxide (alumina) in a cell known as the Hall-Héroult cell.

the ease of obtaining metals from their ores is influenced by their position in the reactivity series. The extraction of iron from hematite involves a series of steps in the blast furnace, including the burning of coke, reduction of carbon dioxide, reduction of iron(III) oxide, thermal decomposition of limestone, and the formation of slag. Aluminium is mainly extracted from bauxite through electrolysis.

Properties of Metals (9.1.1) | CIE IGCSE Chemistry Revision Notes 2023 | Save My Exams

Summary:

In this comprehensive guide, you’ll delve into the world of metal science, exploring properties, uses, alloys, reactivity series, corrosion prevention, and extraction methods. Tailored for chemistry exam preparation, this journey equips you with essential knowledge on metals, their applications, and the intricate processes that govern their behaviour. From the unique characteristics of metals to practical applications like aircraft manufacturing and electrical wiring, each section unfolds key insights.

The guide serves as a valuable resource to aid your understanding of essential concepts and excel in your chemistry exam preparation.