Preliminary
Chemistry
Metals
Lesson 1:
History of Metals and Alloys
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LESSON 1: Metals
Preliminary CHEMISTRY
Summary of Key Words
Account
Account for: state reasons for, report on. Give an account of: narrate a series of events or
transactions
Analyse
Identify components and the relationship between them; draw out and relate implications
Apply
Use, utilise, employ in a particular situation
Assess
Make a judgement of value, quality, outcomes, results or size
Calculate
Ascertain/determine from given facts, figures or information
Clarify
Make clear or plain
Classify
Arrange or include in classes/categories
Compare
Show how things are similar or different
Construct
Make; build; put together items or arguments
Contrast
Show how things are different or opposite
Deduce
Draw conclusions
Define
State meaning and identify essential qualities
Demonstrate
Show by example
Describe
Provide characteristics and features
Discuss
Identify issues and provide points for and/or against
Distinguish
Recognise or note/indicate as being distinct or different from; to note differences between
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LESSON 1: Metals
Preliminary CHEMISTRY
Evaluate
Make a judgement based on criteria; determine the value of
Examine
Inquire into
Explain
Relate cause and effect; make the relationships between things evident; provide why
and/or how
Extract
Choose relevant and/or appropriate details
Extrapolate
Infer from what is known
Identify
Recognise and name
Interpret
Draw meaning from
Investigate
Plan, inquire into and draw conclusions about
Justify
Support an argument or conclusion
Outline
Sketch in general terms; indicate the main features of
Predict
Suggest what may happen based on available information
Propose
Put forward (for example a point of view, idea, argument, suggestion) for consideration or
action
Recall
Present remembered ideas, facts or experiences
Recommend
Provide reasons in favour
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LESSON 1: Metals
Preliminary CHEMISTRY
Lesson Dotpoints
By the end of the lesson, you should understand the following concepts:
History of metals
Outline and examine some uses of different metals through history, including
contemporary uses, as uncombined metals or as alloys
Analyse information to relate the chronology of the Bronze Age, the Iron Age
and the modern era and possible future developments
Identify why there are more metals available for people to use now than there
were 200 years ago
Extracting Metals
Explain why energy input is necessary to extract a metal from its ore
Producing Alloys
Describe the use of common alloys including steel, brass and solder and
explain how these relate to their properties
Gather, process, analyse and present information from secondary sources on
the range of alloys produced and the reasons for the production and use of
these alloys
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LESSON 1: Metals
Preliminary CHEMISTRY
1. The History of Metals
CHECKPOINT:
Outline and examine some uses of different metals through history, including
contemporary uses, as uncombined metals or as alloys
Analyse information to relate the chronology of the Bronze Age, the Iron Age and
the modern era and possible future developments
Identify why there are more metals available for people to use now than there
were 200 years ago
Metals Through History
Gold was the earliest of the metals to be discovered (Stone age), and people
used it to make jewelry.
-
Explain why the use of gold was limited.
Copper was the first metal used to make tools and weapons as it was stronger
and harder then gold
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LESSON 1: Metals
-
Preliminary CHEMISTRY
Define annealing and explain why it was used on copper.
Smelting of Copper and other Metal Ores
Smelting is process where the ore is reduced through used a reducing agent
-
For smelting copper the reducing agent was charcoal
-
Explain how charcoal reduces copper on an atomic level.
The chemical equation for smelting copper is:
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LESSON 1: Metals
Preliminary CHEMISTRY
Applications 1.1
Question 1
Name 2 early metals used by humans and assess the reason for their uses.
(3 marks)
Question 2
Explain why smelting is a chemical process. (2 marks)
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LESSON 1: Metals
Preliminary CHEMISTRY
The Bronze and Iron Age
Bronze Age
Bronze is an alloy – a mixture of copper and tin
Discuss why bronze is more superior then copper in building weapons.
Bronze with 10% tin had a melting point of 950℃
Copper had a melting point of 1083℃
Recasting and the shaping of bronze was easier then copper
Iron Age
During the middle ages the use of bronze declined as the technology for
producing iron became more efficient and cheaper
How do we produce iron?
-
𝐹𝑒2 𝑂3 (Hematite) can be reduced by carbon at temperatures above 1100℃
1. Carbon monoxide is produced by reacting charcoal with oxygen
𝟔𝑪(𝒔) + 𝟑𝑶𝟐(𝒈) → 𝟔𝑪𝑶(𝒈)
2. The carbon monoxide reacts with the hematite to form:
Producing iron ore was common in 1200BC
To produce the high temperatures required workers forced air into the kiln to
encourage more rapid burning and therefore a faster release of heat
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LESSON 1: Metals
Preliminary CHEMISTRY
Applications 1.2
Question 1
Justify why bronze was more commonly used then copper to produce weapons.
(2 marks)
Question 2
Discuss why Iron became the more favoured then bronze. (2 marks)
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LESSON 1: Metals
Preliminary CHEMISTRY
Metals in the Last 200 Years
There are three main reasons why there are more metals were discovered in
the last 200 years then ever before:
Technology
-
High temperature environments could be created to extract metals that
couldn’t be previously extracted
-
Decomposition through electrolysis was discovered by Sir Humphrey Davy
-
Before 1800, the main method to produce relatively high temperatures was
carbon heating but these temperatures are not enough to produce the
metals of today
Metallurgy
-
The improvement of metallurgical skills for making and testing new alloys
led to the incorporation of a wider range of metals into everyday products
-
Scientists began to experiment with different metals to determine the
outputs if two metals were combined e.g Titanium
-
Titanium was not widely used on it’s own as a metal but when it was
discovered that when titanium is combined with limited amounts of other
metals, it becomes extremely hard, has high-tensile strength and is very
light, its use expanded rapidly.
-
Titanium alloys became the back-bone of modern jet and aircrafts. With the
improvement of metallurgical skills to create new alloys, a wider range of
metals are available
Costs
-
In the past it was relatively expensive to extract metals from their ores
-
An example of this can be seen with aluminium. The major cost in extracting
aluminium is the electricity used for the electrolysis and for keeping the
electrolyte molten
-
During the twentieth century the price of electricity fell steadily and this
improved the competitive position of aluminium relative to steel, so it
became used more prominently
-
Thus the reducing cost of extracting the metal is another reason why more
metals are available for people to use now.
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LESSON 1: Metals
Preliminary CHEMISTRY
Question 1 (5 marks)
Assess the reasons for why more metals were discovered in the last 200 years then
in the last 2000 years. (5 marks)
Student Answer:
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LESSON 1: Metals
Preliminary CHEMISTRY
Sample Answer:
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LESSON 1: Metals
Preliminary CHEMISTRY
2. Extracting Metal
CHECKPOINT:
Explain why energy input is necessary to extract a metal from its ore
Definitions
Define the following terms:
-
Ore
-
Mineral
-
Alloy
There are three steps in extracting a metal from ore:
1. Identification of metal ore deposit
2. The metal ore is mined
3. The metal ore is processed in which the metal is separated from the ore
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LESSON 1: Metals
Preliminary CHEMISTRY
What are two main methods of extracting metal from ore?
Properties of Metal
Energy is required to break bonds and to understand how metal ores break
bonds we need to look at the chemical property of metals:
-
How many valency electrons do metals have?
-
Why are some metals found in combined and uncombined forms?
-
When do metals become positive ions?
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LESSON 1: Metals
Preliminary CHEMISTRY
Applications 1.3
Question 1
Draw a labeled diagram of what happens to metals when energy is absorbed and
released.
Question 2
a) When metals are smelted is it an oxidisation or reduction reaction? (1 mark)
b) Do you lose or gain electrons during reduction? (2 marks)
c) How are metals reduced during smelting and is energy released or used?
(1 mark)
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LESSON 1: Metals
Preliminary CHEMISTRY
3. Producing Alloys
CHECKPOINT:
Describe the use of common alloys including steel, brass and solder and explain
how these relate to their properties
Gather, process, analyse and present information from secondary sources on the
range of alloys produced and the reasons for the production and use of these
alloys
Alloys
An alloy is a ________________________________ of a metal with __________ or more
elements
List some examples of alloys
Alloys are formed by mixing substances together through a process of melting
and cooling
-
Are solid alloys homogenous or heterogeneous mixtures?
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LESSON 1: Metals
Preliminary CHEMISTRY
Physical Properties of Alloys
The above diagram shows different types of alloys. Determine how they relate
to the physical properties of alloys.
The advantages of alloys over pure metals include:
1. Harder
2. Resist Higher Temperatures
3. Resists Corrosion
4. High Tensile Strengths
A disadvantage is that alloys are more brittle then pure metal
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LESSON 1: Metals
Preliminary CHEMISTRY
Uses of Alloys
Fill in the rest of the table.
Alloy
Composition
(%)
Structural
Steel
99.8% Fe
0.2% C
Stainless
Steel
10-20% Cr
5 – 20% Ni
70 – 80% Fe
Properties
Hard
High Tensile Strength
Uses
Railways
Beams
Hard
Resists Corrosion
Shiny
Brass
50 – 60% Cu
40 – 50% Zn
Musical
Instruments
Decorations
Door Knobs
Bronze
80 – 90% Cu
10 – 20% Sn
Ship propellers
Statues
Door frames
Solder
30 – 60% Sn
40 – 70% Pb
18 Carat
White
Gold
75% Au
25% Platinum
Copper –
Nickel
Alloy
75% Cu
25% Ni
Low melting point
Adheres to other
metals when in molten
form
Jewellery
Silvery appearance
Resists corrosion
Shiny
From the above table it can be concluded that alloys are ‘designed’ and can be
made depending on its uses
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LESSON 1: Metals
Preliminary CHEMISTRY
Applications 3.1
Question 1
Which of the following properties most directly affects the reactivity of a metal?
a)
b)
c)
d)
Malleability
Melting Point
First Ionisation Energy
Electrical Conductivity
Question 2
Which of these is not an alloy?
a)
b)
c)
d)
18 Carat Gold
Aluminium
Steel
Solder
Question 3 (Exam Choice 2009 – Qu 9)
Identify the correct statement about aluminium.
a) Aluminium is a renewable resource because its ore, bauxite, is formed
continuously by natural geological processes
b) Aluminium mining and extraction consumes very little energy, and hence
makes only a small contribution to the enhanced greenhouse effect
c) One of the most important reasons for recycling aluminium is that it consumes
approximately 20% of the energy required to obtain it from its ore
d) Aluminium production is sufficiently inexpensive that there is no demand for
more expensive recycled material
Question 4
Compare the use of alloys and pure metals in relation to their properties. (3 marks)
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LESSON 1: Metals
Preliminary CHEMISTRY
Question 5
Explain why steel is suitable in making railways. (2 marks)
Question 6
Describe the properties and uses of an alloy. (3 marks)
Question 7 (James Ruse Half Yearly 2002 – Qu 7)
a) Write a balanced chemical equation showing the extraction of an ancient metal.
(1 mark)
b) Australia is the world’s third largest producer of lead. Huge smelters are located
at Mt Isa, Q and Port Pirie, SA where lead is extracted from lead (II) sulfide.
Identify an environmental problem associated with this process. (1 mark)
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LESSON 1: Metals
Preliminary CHEMISTRY
c) Explain why energy input is necessary to extract a metal from its ore. (1 mark)
d) Alloys of lead are used in the plumbing and electronics industries. Identify a
property of lead alloys, which relates to their use. (1 mark)
e) Pure lead plates immersed in dilute sulfuric acid are used in car batteries to
make electricity. (Write a balanced chemical equation showing the reaction of
lead with sulfuric acid. (1 mark)
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