Preliminary Chemistry

Size: px
Start display at page:

Download "Preliminary Chemistry"

Transcription

1 Name: Preliminary Chemistry Lesson 1: Metals (Theory Booklet)

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 2

3 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 3

4 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 4

5 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 5

6 Define annealing and explain why was it used on copper. Question 1 (3 marks) Name 2 early metals used by humans and assess the reason for their uses. 6

7 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: Question 1 (2 marks) Explain why smelting is a chemical process. 7

8 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? - Fe! O! (Hematite) can be reduced by carbon at temperatures above Carbon monoxide is produced by reacting charcoal with oxygen 6C (s) + 3O 2(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 8

9 Question 1 (2 marks) Justify why bronze was more commonly used then copper to produce weapons Question 2 (2 marks) Discuss why Iron became the more favoured then bronze. 9

10 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. 10

11 Question 1 (5 marks) Assess the reasons for why more metals were discovered in the last 200 years then in the last 2000 years. 11

12 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 12

13 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? 13

14 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? b) Do you lose or gain electrons during reduction? c) How are metals reduced during smelting and is energy released or used? 14

15 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? 15

16 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 16

17 Uses of Alloys Fill in the rest of the table. Alloy Composition (%) Properties Uses Structural Steel 99.8% Fe 0.2% C Hard High Tensile Strength Railways Beams Stainless Steel 10-20% Cr 5 20% Ni 70 80% Fe 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 Low melting point Adheres to other metals when in molten form 18 Carat White Gold 75% Au 25% Platinum Jewellery Copper Nickel Alloy 75% Cu 25% Ni 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 17

18 Applications 3.1 Multiple Choice 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 18

19 Short Answer Question 1 Compare the use of alloys and pure metals in relation to their properties. (3 marks) Question 2 Explain why steel is suitable in making railways. (2 marks) Question 3 Describe the properties and uses of an alloy. (3 marks) 19

20 Question 4 (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) 20