Materials

1. Materials School Certificate Topic

2. Outcomes • a) identify that a new compound is formed by rearranging atoms rather than by creating matter x • b) classify compounds into groups based on common chemical characteristics • c) construct word equations from observations and written descriptions of a range of chemical reactions

3. d) identify a range of common compounds using their common names and chemical formulae e) qualitatively describe reactants and products in the following chemical reactions: i) combustion x ii) corrosion iii) precipitation x iv) acids on metals and acids on carbonates v) neutralisation vi) decomposition x f) describe the role of indicators. x

4. Reactants Products Combustion Corrosion Precipitation Carbonate Acid alkali Neutralisation Decomposition Indicator chemical Formulae Equation Element compound Spelling Words

5. Materials – An Introduction For most of the nineteenth century, products were made out of naturally occurring materials. Billiard balls, for example, were made out of the ivory from elephant tusks. In 1869, John Hyatt developed an alternative for ivory, called “celluloid”. This was the first commercially produced artificial plastic. In 1884, Louis Bernigaut used the same substance to make shiny fibres/threads. This was called “rayon”. At the same time photographic film was also made using Hyatt’s celluloid. In 1907, “Bakelite” was made. This is a mouldable plastic which can become hard and insoluble after heating. This was useful for moulded insulation, valves, pipes, knobs, buttons, knife handles and even billiard balls.

6. Questions • Outline the reasons why an alternative was needed for using ivory. • Start a timeline to show the development of plastics. Do you know how to do a proper timeline? (You can continue to complete this as we study plastics further.)

7. b) classify compounds into groups based on common chemical characteristics • Renewable and Non renewable • Natural and Synthetic • Organic and Inorganic • Biodegradable and Non biodegradable • Commercially Viable • Minerals • Amorphous • Ionic • Molecular • Acids • bases

8. Elements and Compounds-revision • Materials can be elements or compounds. • Sometimes materials need to be separated from mixtures. • To Do: • Recall the definitions for “element”, “compound”, and “mixture”. • List all of the materials you can think of that are used today. • How can you classify the materials used into two main groups? (Hint: Think back to ivory and plastic) • Draw up a table classifying the materials the class has identified.

9. Metals and Non Metals • Elements can be divided into metals and non metals. So, too, can materials used. • Compare the properties of metals and non metals. (What is a “property” of something?) • To Do: Draw up a table to show the similarities and differences between metals and non metals. This is the most effective way to answer a “Compare” question. Do you know how to draw up a proper table for your School Certificate?

10. Drawing up a Table. • A table should always have a Heading which is relevant to what you want to show. Eg “Properties of Metals and Non Metals” • There should be clear columns and rows. It is best to do this using ruled lines. • Work out how many columns you need. Make sure that they will not be too confusing and shows the relationships clearly. • How many rows do you need? Do not forget the row for the headings. • Fill in the information. If it is not making sense/ getting too complicated, or you are repeating the same thing over and over (particularly units of measurement) work out how to simplify it and fix this. • So … for the task you have to do… there can be many different ways to complete this task and get full marks in your examination. Have a go. Check with others in the class.

11. Properties of Metals and Non Metals

12. Metals as Materials • Pure Metals – eg. Gold, Copper, Aluminium. Not many can be used in this form because they are usually too soft, expensive, reactive or will corrode. (What does this term mean? • Alloys – a metal combined with one or more other elements. (forming a compound) The properties of the alloy made are different from the original base metal used. Eg. Brass – base metal is copper; Steel = iron +small amounts of carbon. The more carbon added, the stronger that type of steel will be (plus also more expensive) • Native metals – metals that are in their natural state when mined. Eg gold, silver, platinum and copper. They are found this way because they are unreactive. (Think back to Year 9 Reactions topic) • Ores – when the metal is found as a compound (in the minerals in rocks) and is economically viable to mine. eg – aluminium from bauxite (aluminium oxide). The ore needs to be extracted and then processed to separate the metal from the rock.

13. Copy this table down. Can you see any trends?

14. d) identify a range of common compounds using their common names and chemical formulae Copy this table into your book

15. Metals In The Crust Metals make up only a quarter of the Earth’s crust. Oxygen and silicon make up the rest. Oxygen is by far the most abundant, being combined with metals as oxides or with silicon as silicon dioxide in sand or silicates Skill: Now convert the pie chart into a table in your book.

16. Skill – Drawing up a Pie Chart • The diagram on the other slide showed a pie chart. • What is a pie chart? • How can you draw one in a Science exam? Pie charts are a mandatory skill for you to know for your School Certificate so lets make sure you can draw one properly. Pie charts show relative percentages or proportions of a whole. In other words, it is showing the fraction that each factor makes up as a percentage of all that is available, or counted.

17. Drawing a Pie Chart • Use a compass to draw a circle. (Yes you will need to bring one to your exams.) • How many degrees in a circle? Work out roughly (but as accurately as possible) the fraction that each factor makes up in the pie. Do you need a hand with working out fractions? ASK NOW. • Calculate the number of degrees this fraction is equal to. NEED A HAND? • Using a protractor (yes you need one of these as well) work out where to draw each sector line, and draw these in, using a ruler. • Now – this is the part most students forget – MAKE UP A KEY – showing each factor and the colour/pattern that indicates each one. • Eg. = aluminium • Now colour each section . • NOW DRAW THE PIE CHART FOR THE ABUNDANCE OF METALS IN THE EARTH’S CRUST, USING THE TABLE YOU MADE EARLIER.

18. Minerals Used in Everyday Life • How many household products are made of a single mineral? Which ones are combinations? • About how many minerals are needed to make a computer? Why? • What is the most prevalent mineral/material in items in an office? Are you surprised by it? Research this material and find out all of the products that it makes. What would happen if we run out of it? • Where do most of the minerals found in a house come from? • Think about all of the mining and drilling necessary to create these products we use every day. What does this indicate about the mining industry?

19. Minerals And Ores • All other metals are found combined with other elements as compounds. Minerals are rocks containing large amounts of a particular metal. If there is sufficient metal to make it worth mining, it is called an ore. Mining produces valuable metals and creates jobs. Sometimes, however, mining is not worth its expense or the negative effects on society and the environment.

20. Mining for Minerals Even though minerals are very useful as materials, the processes needed to recover them, and refine them present problems for the environment. • Why does gold sink to the bottom when miners "pan" for gold? • Describe the tools and engineering challenges of making a shaft mine safe for mineral extraction by miners. • How is gypsum transformed into building materials? Can you name other minerals that you have in your home that were recovered through mining? • Are mined materials renewable or non-renewable resources?

21. Mining for Ores Underground mines are used for the mining of deep ores but water penetration, possible collapse, venting of poisonous and explosive gases and the provision of fresh air for the miners are problems that must be managed. If the ore is close to the surface, open-cut mining is easier. An overburden of soil is removed and the ore is dredged out, creating benches, or steps that spiral into the hole. These are also used as access roads to haul the ore to the surface by truck. Open-cut mines cause problems including unsightliness, pollution of surrounding areas with dust, pooling of water, destruction of land above the ore, and the need to repair the land after mining ceases. COMPARE open cut and underground mining. HINT: A table is usually the clearest way to answer a “Compare” question (show similarities and differences)

22. The Mining Process Before mining begins, we need to know: • How much ore is there and how concentrated is it? • How deep is the ore? What type of mine is needed? • Is the site close to existing ports and rail lines? • Which workers can be employed? • Who owns or controls the land? • What water and air pollution will it cause?• What damage will be done to the environment • What is the cost of building the mine and the processing plants, and repairing the environmental damage? • What is the current and expected future price of the metal? • What profit is expected?

23. Concentration Of The Ore Impurities and waste called gangue are mined with the ore. The mined material is crushed by rollers or by large steel balls that fill a large rotating drum called a ball mill. Gravity and sieves separate some of the gangue, with the remainder then separated by froth-flotation. This is a technique pioneered in Broken Hill, in which the crushed ore floats away on a frothy emulsion of oil and water, leaving the gangue behind. The ore is now ready for extraction.

24. Separating Metals from their Ores Electrolysis • Electrolysis uses a huge amount of electricity and is used only when there is no cheaper method available. • A voltage is applied to a molten sample or solution of the ore and the positive metal ions move to the negative electrode. When it gets there, the ion is forced to take back its outer-shell electrons to form metal atoms that then plate the electrode. Sodium is extracted from rock salt by this method. FIRST – Lets revise the structure of the atom, particularly shells and charges of particles. Do you remember how atoms gain an overall charge? What does this look like?

25. A Diagram of Electrolysis for you to copy.

26. PRACTICAL Electrolysis

27. EXTENSIONCase Study of Electrolysis. • Sodium (NaCl) is made by electrolysis of sea water or, rock salt. The salt is melted to break the salt crystals into its ions, then converted into pure elements by electrolysis. • At the negative electrode: Na+ + e– -------- Na • and at the positive electrode: 2Cl– --------- Cl2 + 2e- • Overall, 2NaCl(l)---------- 2Na(l) + Cl2(g)

28. Separating Metals from their Ores Heat • Heat is sometimes enough energy to extract the pure metal. This is called smelting. • The more reactive metals such as lead, iron and zinc need carbon or carbon monoxide (CO) to help the conversion along. • To extract iron, coke (a source of carbon), limestone (CaCO3) and iron ore (Fe2O3) are heated in a blast furnace. What does this look like?

30. EXTENSIONCase Study of Heat • Smelting of iron occurs as a series of chemical reactions. First the coke reacts to form carbon dioxide: • First the coke reacts to form carbon dioxide: C(s) + O2(g)-------- CO2(g) • Limestone then decomposes, forming calcium oxide and more carbon dioxide: CaCO3(s)--------- CaO(s) + CO2(g) • Carbon dioxide reacts with more coke, forming carbon monoxide: CO2(g) + C(s)--------- 2CO(g) • This reacts with the iron ore to form molten iron, which then runs to the bottom of the furnace: Fe2O3(s) + 3CO(g)--------- 2Fe(l) + 3CO2(g)

31. Waste calcium oxide reacts with sand in the iron ore, forming calcium silicate: • CaO(s) + SiO2(s)-------- CaSiO3(l) • Calcium silicate is called slag and floats on the molten iron. • More stable metals only need roasting in air. Most copper is extracted by roasting copper(I) sulphide, found in an ore called copper pyrites: • Cu2S(s) + O2(g)-------- 2Cu(l) + SO2(g)

32. Case Studies in Materials • Copy this table into your book. You will use one of these for each case study completed.

33. Materials Used in Medicine

34. Materials for Joint Replacement in Humans • Generally, the most common materials used in orthopaedic implants are metals and a type of plastic called polyethylene.  These two material types are combined in most joint implants, that is, one component is made from metal, and one from polyethylene. When properly designed and implanted, the two components can rub together smoothly while minimizing wear.  • While some pure metals have excellent characteristics for use as implants, most metal implants are made from a mixture of two or more metals. These mixed metals are called alloys. By combining metals, a new material can be created that has a good balance of the desired characteristics. The most common metal alloys used in orthopaedic implants are stainless steels, cobalt-chromium alloys, and titanium alloys.

35. Materials Used in Implants • Draw up a table to COMPARE the materials used in surgical replacements. • The headings should be – • Name of material • Type of material • Composition • Properties • Uses

36. Metals Used in Implants Stainless Steel • Stainless steel is a very strong alloy, and is often used in implants to help repair fractures, such as bone plates, bone screws, pins, and rods.  • Stainless steel is made mostly of iron, with other metals such as chromium or molybdenum added to make it more resistant to corrosion. • There are many different types of stainless steel. The stainless steels used in orthopaedic implants are designed to resist the normal chemicals found in the human body.

37. Cobalt-chromium Alloys Cobalt-chromium alloys are also strong, hard, biocompatible, and corrosion resistant. These alloys are used in a variety of joint replacement implants, as well as some fracture repair implants, that require a long service life. While cobalt-chromium alloys contain mostly cobalt and chromium, they also include other metals, such as molybdenum, to increase their strength Parts used in a hip replacement.

38. Titanium Alloys Titanium alloys are considered to be biocompatible.  They are the most flexible of all orthopaedic alloys. They are also lighter weight than most other orthopaedic alloys.  Consisting mostly of titanium, they also contain varying degrees of other metals, such as aluminum and vanadium. Titanium Pure titanium may also be used in some implants where high strength is not required. It is used, for example, to make fiber metal, which is a layer of metal fibers bonded to the surface of an implant to allow the bone to grow into the implant, or cement to flow into the implant, for a better grip. Tantalum Tantalum is a pure metal with excellent physical and biological characteristics. It is flexible, corrosion resistant, and biocompatible

39. Problem with Using Metals #1- The Activity Series • Experiment. Add a small piece of magnesium to dilute hydrochloric acid. Note the reactivity. Repeat with iron and copper. Record your results in a table. • Metals vary in their reactivity with other substances. Eg magnesium( ) reacted vigorously with dilute HCl, iron ( ) bubbled slowly and copper ( ) didn’t react at all.

40. PRACTICAL Activity Series of Metals • Aim: to see which is the most reactive metal magnesium, iron or copper. • Materials: 3 test tubes, test tube rack, small clean pieces of Mg, Fe and Cu, solutions of magnesium nitrate, iron nitrate and copper nitrate. • Method: • Add a small piece of Mg to 3 test tubes. Add

41. Results • Rule up a table to record your results. Discussion questions. • Which metal reacted with all of the solutions? Write word equations to show these reactions. • Which metal reacted with none of the solutions? • Which is the most reactive metal? Least reactive? Conclusion List the metals in order from most to least reactive.

42. Activity Series • Using large numbers of metals and their solutions, chemists have come up with a list of metals from most to least reactive. • This is done by studying the results of displacement reactions. • A more reactive metal will displace a less active metal from solution. • Sodium + copper nitrate → sodium nitrate + copper

43. Some metals lose their electrons more easily than others. These metals are reactive and are harder to extract. Different extraction techniques are required, depending on the metal’s position in the activity series.

44. Look at this table – summarise the trends.

45. Activity Series – A Summary of Trends As we move up the activity series: • the chance of metals reacting with chemicals becomes greater • the metals become less stable • there is less chance of finding the metals in their natural state • the compounds of the metals become more stable and more difficult to break down • the extraction process becomes more difficult and more expensive. Eg sodium needs to be extracted by electrolysis whereas lead is extrcted by smelting. Gold and silver are found as metals in nature as they are unreactive.

46. Processing of Materials to Make Implants for Surgical Procedures.

47. PlasticsPolyethylene • Polyethylene is a type of plastic commonly used on the surface of one implant that is designed to contact another implant, as in a joint replacement. • Polyethylene is also the material used to make milk cartons but he polyethylene used in orthopaedic implants is a much higher grade. In fact, a special type of medical-grade polyethylene was developed specifically for use in orthopaedic implants.  • Polyethylene is very durable when it comes into contact with other materials. When a metal implant moves on a polyethylene surface, as it does in most joint replacements, the contact is very smooth and the amount of wear is minimal.    • Patients who are younger or more active may benefit from polyethylene with even more resistance to wear. This can be accomplished through a process called crosslinking, which creates stronger bonds between the elements that make up the polyethylene. The appropriate amount of crosslinking depends on the type of implant. For example, the surface of a hip implant may require a different degree of crosslinking than the surface of a knee implant.

48. Ceramics Ceramic materials are usually made by pressing and heating metal oxides (typically aluminium oxide and zirconium oxide) until they become very hard. These ceramic materials are strong, resistant to wear, and biocompatible. They are used mostly to make implant surfaces that rub together but do not require flexibility, as in the surfaces of a hip joint.

50. Composites • Composite materials are made by mixing two or more separate materials without creating a chemical bond between the materials. For example, carbon fibres may be added to another material to provide additional strength, but the two materials do not combine in a way that creates a new material. Metal alloys and ceramics are not considered to be composite materials because their ingredients are chemically bonded to create a new material.  • On a larger scale, two layers of different materials can be combined to create a composite material with the desired characteristics. The stem of a hip implant, for example, may consist of layers of two different materials that together provide the desired combination of strength and flexibility.