Metal and their uses

For nearly 600 years, cathedrals were the tallest human-made structures on Earth.
- Constructed primarily from wood and stone.
- Size limitations were based on material properties rather than builders' creativity.
The Eiffel Tower opened in 1889 and became the tallest structure, surpassing 300 meters in height.
  - This height is twice that of any previous buildings.
  - Primarily constructed from iron, enabling structural components to be strong and stiff.
  - Iron could be shaped into girders and rolled into sheets, allowing for versatile construction.

Lincoln Cathedral's spire (160 meters) was the tallest human-made structure from 1311 until it collapsed in 1549.
Comparison of building heights through history:
- Chart indicating progressive structure heights leading to modern skyscrapers, ending with the Burj Khalifa at 830 meters, completed in 2009.
Diagram B illustrates tallest buildings:
- Giza Pyramid, Lincoln Cathedral, Eiffel Tower, Empire State Building, Taipei 101, Willis Tower, Burj Khalifa.
Question: Why was iron not used in earlier buildings in the 1300s?

New material technologies have revolutionized construction:
  - Steel replaced iron due to improvements in metallurgy.
  - Various metals find specific applications (e.g., lead for roofs, aluminum for windows, titanium for pipes).
  - Contemporary "supertall" buildings utilize composite materials for improved strength-to-weight ratios.

Two key properties of iron suitable for tall structures:
1. Strength to withstand compressive loads.
2. Malleability for various shapes and forms.

Besides iron, three other metals are commonly used:
  - Copper: Utilized in electrical wiring for its excellent conductivity.
  - Aluminum: Used for its light weight and resistance to corrosion in window frames.
  - Lead: Commonly used for roofing joints primarily due to its malleability.

Historically, gold and silver were not used for tall structures likely due to:
- Cost and malleability issues, making them impractical for structural purposes.

Advantage: Increased usable floor space in urban areas.
Disadvantage: Higher construction and maintenance costs, including structural integrity concerns during stresses like wind.

Metals are defined as elements distinguished by common physical properties:
  - Malleable (can be hammered into shape)
  - Ductile (can be stretched)
  - Good conductors of heat and electricity
  - Shiny (when polished)

Four physical properties:
  1. Good conductivity for both heat and electricity.
  2. Malleability and ductility.
  3. Lustrous appearance.
  4. High tensile strength.

Specific unusual elements:
- Liquid Metal: Mercury, which remains liquid at room temperature.
- Conductive Non-Metal: Graphite, known for its electrical conductivity.

Metals can react with oxygen:
  - Example reactions:
    1. Lithium + Oxygen → Lithium Oxide
    2. Zinc + Fluorine → Zinc Fluoride
Reaction variations depend on the metal's properties and the speed of reactions. For instance:
- Sodium reacts rapidly with oxygen and burns brightly, producing sodium oxide.
- Magnesium reacts with chlorine gas but at a relatively slower pace.

Catalysts speed up chemical reactions without undergoing permanent changes themselves.
Copper can be used as a catalyst to accelerate hydrogen production from zinc and sulfuric acid:
- Reaction: Zinc + Sulfuric Acid → Zinc Sulfate + Hydrogen (with copper catalyst).
- Catalysts can be recovered and reused due to their unchanged state post-reaction.

Rust, a common issue for iron structures, results from corrosion, specifically an oxidation reaction with moisture and oxygen:
- Rusting of Iron: Requires both oxygen and water (iron hydroxide being produced).
Prevention Methods: Coating iron with barriers such as paint protects against rusting:
  1. Paint (within 30 years lifespan).
  2. Plastic coatings.
  3. Oil or powder coatings.

Some reactive metals (lithium, sodium, potassium) react with cold water:
- Sodium + Water → Sodium Hydroxide + Hydrogen
Properties of reactive metals:
- Metal X is likely to be positioned towards the top of the reactivity series, indicating a strong propensity for reaction with water and acids.

Establishing a hierarchy for metals regarding their reactivity assists in predicting chemical behavior:
- Order includes: Potassium > Sodium > Lithium > Calcium > Magnesium, and less reactive metals like Tin and Lead.

High-quality evidence must be both accurate (close to the real value) and reliable (repeatable and reproducible).
Accuracy relies on the measuring device used, variable control, and skill of experimenters.

Typical reaction of metal + acid yields a salt and hydrogen gas:
- Example: Magnesium + Hydrochloric Acid → Magnesium Chloride + Hydrogen.
- Acid rain can significantly accelerate rusting rates in iron structures.

Alloys are metallic mixtures with tailored properties:
- Bronze (copper and tin) is harder than pure metals.
- Other examples include Stainless Steel (iron, nickel, chromium).

Investigating new alloys often involves considerations of weight, strength, and corrosion resistance, particularly in industrial applications such as construction and durable goods.

Metals are utilized in public art to improvise both aesthetics and durability:
- Sculptures like the Kelpies (coated in zinc) exemplify how coatings can inhibit rusting.
The use of alloys allows for functional and attractive public works of art.