Preliminary Chemistry - Synergy Education · 2017-11-02 · Preliminary Chemistry Metals Lesson 1: History of Metals and Alloys 0466 342 939 [email protected] Name: _____

Preliminary Chemistry

Metals

Lesson 1: History of Metals and Alloys

0466 342 939 [email protected] www.synergyhsc.com

Name: _____________________

LESSON 1: Metals Preliminary CHEMISTRY

Copyright © HSC Synergy Education 2015 2

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



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



Lesson Dotpoints By the end of the lesson, you should understand the following concepts: History of metals x Outline and examine some uses of different metals through history, including

contemporary uses, as uncombined metals or as alloys x Analyse information to relate the chronology of the Bronze Age, the Iron Age

and the modern era and possible future developments x Identify why there are more metals available for people to use now than there

were 200 years ago Extracting Metals x Explain why energy input is necessary to extract a metal from its ore Producing Alloys x Describe the use of common alloys including steel, brass and solder and

explain how these relate to their properties

x 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



1. The History of Metals

CHECKPOINT:

Metals Through History

x 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.

x Copper was the first metal used to make tools and weapons as it was stronger

and harder then gold

x Outline and examine some uses of different metals through history, including contemporary uses, as uncombined metals or as alloys

x Analyse information to relate the chronology of the Bronze Age, the Iron Age and the modern era and possible future developments

x Identify why there are more metals available for people to use now than there were 200 years ago



- Define annealing and explain why it was used on copper.

Smelting of Copper and other Metal Ores x 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:



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)



The Bronze and Iron Age Bronze Age x Bronze is an alloy – a mixture of copper and tin x Discuss why bronze is more superior then copper in building weapons.

x Bronze with 10% tin had a melting point of 950℃

x Copper had a melting point of 1083℃ x Recasting and the shaping of bronze was easier then copper Iron Age

x During the middle ages the use of bronze declined as the technology for

producing iron became more efficient and cheaper

x How do we produce iron?

- 𝐹𝑒2𝑂3 (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:

x Producing iron ore was common in 1200BC

x To produce the high temperatures required workers forced air into the kiln to

encourage more rapid burning and therefore a faster release of heat



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)



Metals in the Last 200 Years x 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.



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:



Sample Answer:



2. Extracting Metal

CHECKPOINT:

Definitions

Define the following terms: - Ore

- Mineral

- Alloy

x 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

x Explain why energy input is necessary to extract a metal from its ore



x What are two main methods of extracting metal from ore?

Properties of Metal

x 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?



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)



3. Producing Alloys

CHECKPOINT:

Alloys x An alloy is a ________________________________ of a metal with __________ or more

elements

x List some examples of alloys

x Alloys are formed by mixing substances together through a process of melting

and cooling - Are solid alloys homogenous or heterogeneous mixtures?

x Describe the use of common alloys including steel, brass and solder and explain how these relate to their properties

x 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



Physical Properties of Alloys x The above diagram shows different types of alloys. Determine how they relate

to the physical properties of alloys.

x The advantages of alloys over pure metals include:

1. Harder

2. Resist Higher Temperatures

3. Resists Corrosion

4. High Tensile Strengths

x A disadvantage is that alloys are more brittle then pure metal



Uses of Alloys

x Fill in the rest of the table.

Alloy Composition (%)

Properties Uses

Structural

Steel

99.8% Fe

0.2% C

x Hard x High Tensile Strength

x Railways x Beams

Stainless Steel

10-20% Cr 5 – 20% Ni

70 – 80% Fe

x Hard x Resists Corrosion x Shiny

Brass

50 – 60% Cu 40 – 50% Zn

x Musical

Instruments x Decorations x Door Knobs

Bronze

80 – 90% Cu 10 – 20% Sn

x Ship propellers x Statues x Door frames

Solder

30 – 60% Sn 40 – 70% Pb

x Low melting point x Adheres to other

metals when in molten form

18 Carat

White Gold

75% Au

25% Platinum

x Jewellery

Copper –

Nickel Alloy

75% Cu 25% Ni

x Silvery appearance x Resists corrosion x Shiny

x From the above table it can be concluded that alloys are ‘designed’ and can be

made depending on its uses



Applications 3.1 Question 1 Which of the following properties most directly affects the reactivity of a metal? a) Malleability b) Melting Point c) First Ionisation Energy d) Electrical Conductivity Question 2 Which of these is not an alloy? a) 18 Carat Gold b) Aluminium c) Steel d) 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)



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)



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)

Documents

Preliminary Chemistry - Synergy Education · 2017-11-02 · Preliminary Chemistry Metals Lesson 1: History of Metals and Alloys 0466 342 939 [email protected] Name: _____