Metals and Their Properties

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Questions and Answers

Which characteristic is NOT typically associated with metals?

Brittleness (correct)

High electrical conductivity

Malleability

Ductility

Which of the following metals is least likely to react with water?

Calcium

Potassium

Aluminum (correct)

Sodium

What is produced when metals react with acids?

Heat and light

Hydrogen gas and a metal salt (correct)

Water and carbon dioxide

Oxygen gas and metal hydroxide

What is a common property of metal oxides formed during the combustion of metals in oxygen?

They are basic Signup and view all the answers

Which of the following metals is known for its high reflectivity of light?

Gold Signup and view all the answers

What is the primary purpose of extractive metallurgy?

To separate valuable minerals from waste rock Signup and view all the answers

Which exception among the listed metals is liquid at room temperature?

Mercury Signup and view all the answers

What is the first process that most ores undergo after mining?

Mineral processing Signup and view all the answers

What happens when a highly reactive metal like sodium reacts with water?

It produces a metal hydroxide and heat Signup and view all the answers

Which refining method oxidizes impurities in a high-temperature liquid bath?

Pyrometallurgical refining Signup and view all the answers

What is the primary metallic building material that has replaced wrought iron since around 1890?

Steel Signup and view all the answers

Which metal was first used as a structural material in a bridge built between 1777-1779?

Cast iron Signup and view all the answers

What characteristic of ferrous metals can be controlled during manufacturing?

Chemical composition Signup and view all the answers

Why do people in the construction field have limited control over ferrous metals?

They cannot improve the quality after fabrication. Signup and view all the answers

What defines the yield stresses of steel as of 1989?

Ranging from 165 – 690 Mpa Signup and view all the answers

What type of iron is produced in a blast furnace?

Pig iron Signup and view all the answers

What is the main purpose of adding coke in the pig iron manufacturing process?

To provide a source of carbon for the iron Signup and view all the answers

What chemical process occurs at approximately 815°C in the blast furnace?

The melting of iron ore, limestone, and coke Signup and view all the answers

Why is pig iron considered weak and brittle despite being very hard?

It contains a high percentage of carbon Signup and view all the answers

What is the main function of the cupola furnace in the manufacturing process?

To re-melt pig iron for casting Signup and view all the answers

What is formed when molten limestone combines with gangue during the iron smelting process?

Slag Signup and view all the answers

How is cast iron primarily categorized?

By its shape and method of production Signup and view all the answers

How is the chemical composition of cast iron adjusted during production?

By introducing scrap iron, steel, silicon, and manganese Signup and view all the answers

What happens to the pig iron after it is produced?

It must be further purified to produce quality iron or steel Signup and view all the answers

What characteristic is prominent in the structure of white cast iron?

Brittle structure Signup and view all the answers

What is an advantage of using gray cast iron?

Excellent machinability Signup and view all the answers

Which type of cast iron is known for having spherical particles during solidification?

Ductile iron Signup and view all the answers

How is malleable cast iron produced from white cast iron?

Through annealing heat treatment Signup and view all the answers

Which of the following properties is NOT associated with gray cast iron?

High strength of 275 Mpa Signup and view all the answers

What is the primary reason ductile iron may be preferred over gray iron despite its higher cost?

Spherical graphite structure Signup and view all the answers

What is a disadvantage of using white cast iron?

It is not easily machined Signup and view all the answers

Which alloying elements are typically found in ductile cast iron?

Manganese and magnesium Signup and view all the answers

What is the primary method by which wrought iron is produced?

Puddling process Signup and view all the answers

Which element is NOT typically found in wrought iron?

Carbon Signup and view all the answers

What is a characteristic feature of wrought iron as compared to cast iron?

Wrought iron becomes stronger with each heating and working Signup and view all the answers

How does cast iron primarily differ from wrought iron in terms of production?

It is made by casting rather than heating and bending Signup and view all the answers

Which of the following components is part of a puddling furnace?

Grate Signup and view all the answers

What describes the slag in wrought iron?

Incorporated but not in chemical union Signup and view all the answers

Why is wrought iron considered stronger than cast iron?

It undergoes repeated heating and working Signup and view all the answers

Which of the following best describes cast iron's resistance under pressure?

Cast iron has a greater capability to resist deformation under pressure Signup and view all the answers

Study Notes

Metals

Metals are substances characterized by high electrical and thermal conductivity, malleability, ductility, and reflectivity.
Common metals in Earth's crust include aluminum, iron, calcium, sodium, potassium, and magnesium.
Most metals are found in ores, but some, like copper, gold, platinum, and silver, are found in their free state because they do not readily react with other elements.

Physical Properties of Metals

Good conductors of heat and electricity.
Ductile (can be pulled into wire).
Malleable (can be pounded into sheets).
Sonorous (produce a deep sound when struck).
Solid at room temperature (except mercury).
Usually shiny with metallic luster.
High melting points.
High density (exceptions: lithium, potassium, and sodium).
Corrode in air or seawater.
Lose electrons in reactions.

Chemical Properties of Metals

React with water: Highly reactive metals react vigorously with water, producing hydrogen gas and significant heat.
React with acids: Metals react with acids, producing hydrogen gas and a salt. Zinc reacting with hydrochloric acid is an example.
React with bases: Some metals react with bases, producing hydrogen gas and a metal salt. Zinc reacting with sodium hydroxide is an example.
React with oxygen: Metals react with oxygen when burned, forming metal oxides. Magnesium reacting with oxygen forms magnesium oxide.

Extractive Metallurgy

Mineral processing: The initial step in separating valuable minerals from the waste rock (gangue) in crude ores.
Extractive metallurgy: This process involves extracting the metal from the chemical compound form and refining it, removing impurities.
Smelting: A process in which all constituents are melted and separated into two liquid layers (valuable metals and waste).
Refining: A process that follows extraction, to further reduce the level of impurities using pyrometallurgical, electrolytic, or chemical methods. Pyrometallurgical refining typically involves oxidizing impurities in a high-temperature liquid bath.

Ferrous Metals

Ferrous metals include iron and steel, which are vital in construction.
Chemical composition and structure of ferrous metals are closely controlled during manufacturing.
Strength and other mechanical properties are highly reliable.
People involved in construction have limited control over the quality of iron/steel after leaving the fabrication shop.

Historical Background

Cast iron was the first metal used for structural purposes (e.g., the 30m arch bridge built in England between 1777 and 1779).
Cast iron bridges were common from 1780 to 1820.
Wrought iron started replacing cast iron after 1840, with the Brittania Bridge (Wales) being an example.
Currently (late 1980s), steels are prevalently used in construction, with yield stresses ranging between 165 and 690 MPa.

Manufacture of Pig Iron

Pig iron is a low-grade iron produced in blast furnaces.
Blast furnaces are tall and wide, continuously loading iron ore, coke, and limestone at the top.
Iron ore is an oxide of iron found in nature and associated with rocks.
Coke is produced by heating coal to remove impurities.
The heat generated from burning coke melts iron ore and limestone to separate iron from impurities that become slag.
The molten pig iron is significantly heavier than slag and collects at the bottom of blast furnaces.

Manufacture of Cast Iron

Cast iron is produced by re-melting pig iron with coke and limestone. A furnace (Cupola furnace) is used for this process. It's similar to a blast furnace, but smaller.
Scrap iron/steel, silicon, and manganese are added to control the chemical composition.
The molten metal is poured into molds, forming various shapes (casting).

White Cast Iron

White cast iron is made by rapidly cooling molten pig iron, combining carbon and iron. The fractured surface is bright white.
It has high strength and is resistant to abrasion.
However, it is very brittle and not easy to machine.
Used in parts like crushers and grinders.

Gray Cast Iron

Gray cast iron is made by slowly cooling molten pig iron, resulting in graphite flakes.
It is highly machinable and resistant to abrasion.
It has a lower ductility and toughness compared to other types.
Frequently used in intricate castings.

Ductile Cast Iron

Ductile (also known as nodular or spheroidal graphite) iron is similar to gray iron but has graphite particles that are spherical.
This significantly improves the ductility and shock resistance compared to gray iron. However, it is more expensive.

Malleable Cast Iron

Malleable cast iron is annealed white cast iron. Annealing transforms the brittle structure to a malleable form. Its composition is similar to white cast iron, but with slightly more carbon and silicon.
Malleable iron is ductile, tough, resistant to corrosion, and machinable.
Used for small castings that need good tensile strength.

Manufacture of Wrought Iron

Wrought iron is a highly refined iron with slag purposely incorporated but not chemically combined with iron.
Slag fibers are uniformly distributed throughout the metal, affecting its final properties.
The puddling process, invented by Henry Cort, was a major development. It involved heating and stirring pig iron with oxidizing substances in a furnace.

Cast Iron vs. Wrought Iron

Cast iron is made through casting, while wrought iron is made via repeated heating and working.
Wrought iron is stronger than cast iron, and can resist deformation under pressure and stress.
Cast iron is easier and cheaper to produce.

Basic Oxygen Process (BOP)

The Basic Oxygen Process is a steelmaking process that uses an oxygen lance to oxidize impurities in the heated molten iron.
Impurities are removed by the slag during the process, helping refine the molten steel. Pig iron acts as fuel during this process.

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Description

Explore the fascinating world of metals, covering their physical and chemical properties. This quiz delves into the characteristics that define metals and their common occurrences in nature. Test your knowledge on conductivity, malleability, and reactivity of various metals!