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Which metals are essential for human health? Do deficiencies of essential trace elements cause any significant human health effects? Which metals are essential for plant health? Are Persistence, Bioaccumulation & Toxicity (PBT) appropriate criteria for ranking the hazards of inorganic metals and metal compounds? Are all metals in the soil and water bioavailable? What are the key steps in the health & ecological risk assessment of chemicals (including metals & metal compounds)? Metals Whole periods of human civilization - such as the Bronze and Iron ages - are named for metals. These were the first materials to be "engineered," that is, people changed them to fit what they needed to do, rather than just letting their natural properties determine what they could be used for. These days, materials scientists are using metals in ways no one could have pictured even a few years ago - for example, shaping copper into tiny wires a thousand times skinnier than a strand of your hair! 1. Why did it take society so long to develop metals? 2. Define an alloy. 3. Why do metals break even though they are not stressed beyond their elastic limit? What conditions cause this type of failure? 4. What would be the advantage of alloys that would withstand higher temperatures? 5. Why does recycling save so much energy? 6. Removing elemental metal from its ore is called._______ 7. What impact does quenching have on ferrous metals? 8. What effect on tensile strength does stretching copper have? 9. Does rusting of steel occur at the anode of cathode? 10. What material is used as a "sacrificial" anode of steel? 11. What metal is alloyed with iron to make stainless steel? 12. What mechanical process is accomplished by stretching copper? 13. What happens to dislocations when a wire is bent? 14. Give the words for the following acronyms: FCC, BCC, HCP. 15. How does the metal composition differ in a paper clip and a bobby pin? 16. Compare the grain differences in normal steel and quenched steel. Answers to Review Questions 1. Why did it take society so long to develop metals. It is very difficult to form elemental metals from their ores. It often requires very high temperatures. The technology for this process took many years to develop. 2. Define an alloy. A substance that has metallic properties and is made up of two or more chemical elements, of which at least one is a metal. The two types of alloys are in 3. Why do metals break even though they are not stressed beyond their elastic limit? What conditions cause this type of failure? Under repetitive stresses, cracks in a metal can develop and grow. 4. What would be the advantage of alloys that would withstand higher temperatures? They could be used for many applications, such as higher temperature gasoline engines, nuclear reactor containment vessels, etc. 5. Why does recycling save so much energy? Because of the large amount of energy required to form elemental metals from their ores. 6. Removing elemental metal from its ore is called Extracting or Reduction . 7. What impact does quenching have on ferrous metals? If the metal contains carbon, the carbon will not be able to separate during the FCC to BCC transition and will be trapped, resulting in a distorted BCC structure. This hard, brittle form of steel is called Martensite. 8. What effect on tensile strength does stretching copper have? Stretching copper increases its tensile strength due to the formation of dislocations which become pinned. 9. Does rusting of steel occur at the anode of cathode? Rusting is an oxidation process and occurs at the anode. 10. What material is used as a "sacrificial" anode of steel? Zinc is used in galvanized steel. 11. What metal is alloyed with iron to make stainless steel? Chromium. 12. What mechanical process is accomplished by stretching copper? Cold-working. 13. What happens to dislocations when a wire is bent? More dislocations form and they get tangled or pinned. 14. Give the words for the following acronyms: FCC, BCC, HCP. FCC - Face centered cubic, BCC - Body centered cubic, HCP - hexagonal closest packed 15. How does the metal composition differ in a paper clip and a bobby pin? The bobby pin contains more carbon and is harder and stronger. 16. Compare the grain differences in normal steel and quenched steel. Normal steel contains separate grains of BCC arranged Fe and Fe3C. In quenched steel, the carbon remains in the BCC iron crystals distorting its structure. What is a metal and what is a heavy metal? The term heavy metal refers to any metallic chemical element that has a relatively high density and is toxic or poisonous at low concentrations. Examples of heavy metals include mercury (Hg), cadmium (Cd), arsenic (As), chromium (Cr), thallium (Tl), and lead (Pb). An alloy is a metal composed of more than one element. Engineering alloys include the cast-irons and steels, aluminum alloys, magnesium alloys, titanium alloys, nickel alloys, zinc alloys and copper alloys. For example, brass is an alloy of copper and zinc. How are metals found in nature? Metals are an integral part of our planet and are found in almost all rocks and soils. Most metals form compounds, called minerals, which are naturally occurring, inorganic solids with regular chemical compositions and crystal structures. Although most metal-bearing mineral compositions comprise several elements, there are a few exceptions such as gold, which is found in its elemental form as a mineral called native gold. Metals can form, or be part of, many different minerals. The number of metals (over 70 in the periodic table) and their compounds results in an enormous array of minerals. Iron, for instance, which is very abundant in nature, is found in over 1100 minerals*. The brilliant colours frequently associated with gems such as emerald, ruby and sapphire reflect the variety of metal-containing minerals. Chalcopyrite, an important copper-bearing mineral, is bright yellow, while the copper-phosphate mineral, turquoise, has a blue colour. Minerals combine to become the rocks that make up our planet. Most rocks form considerably below the surface of the earth under the influence of pressure and heat. Geologic processes can cause them to move upward toward the surface. There, in the presence of oxygen and water, they break down, releasing elements - including metals - into solutions, and forming new minerals. This process, known as weathering, forms our soils. From soil, metals are taken up by plants and then by animals and humans in food. As soils are eroded, metal-bearing sediment is carried into streams and rivers, and eventually into the ocean. These sediments contribute to new rocks through ongoing geologic processes. Metals are ubiquitous in nature, and their distribution in the earth depends on geologic processes that have taken place. Some processes may form minerals with high metal contents; rocks containing these minerals may be so enriched that they can be mined at a profit - becoming ore deposits. Rocks that contain lower enrichments are known simply as mineral deposits. The metal content of deposits can range from a few parts per million (ppm) to as much as 650,000 ppm (65%) in the case of some iron ores. Mining companies employ special technologies to extract metals from complex ores in the production of pure metals such as iron, aluminum, copper and gold. While high concentrations of metals may lead to the formation of deposits, in many cases where the concentration of a metal is low, the metal may simply replace, or substitute for, another element in the crystal structure of common minerals. For example, rocks that make up the sea floor contain high concentrations of the metal magnesium, as well as smaller concentrations of nickel which substitute for some of the magnesium. Similarly, rocks that make up the continents can contain lead, which substitutes for the more abundant metallic element, potassium. This substitution phenomenon leads to the wide distribution of many metals at low concentrations throughout the rocks of the earth. Natural geologic processes continue at a very slow pace to concentrate and disperse metals, forming large zones of elevated metal concentrations and constantly releasing metals into the environment. A full understanding of these natural processes and the resulting metal dispersion patterns is important in the discovery and recovery of metals and for determining the impact of metals in the environment. What are some applications of metals? How are metals found in nature? Metals are opaque, lustrous elements that are good conductors of heat and electricity. Most metals are malleable and ductile and are, in general, denser than the other elemental substances. |
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What are some applications of metals? Metals are used in: * Transportation -- Cars, buses, trucks, trains, ships, and airplanes. * Aerospace -- Unmanned and manned rockets and the space shuttle. * Computers and other electronic devices that require conductors (TV, radio, stereo, calculators, security devices, etc.) * Communications including satellites that depend on a tough but light metal shell. * Food processing and preservation -- Microwave and conventional ovens and refrigerators and freezers. * Construction -- Nails in conventional lumber construction and structural steel inother buildings. * Biomedical applications -- As artificial replacement for joints and other prostheses. * Electrical power production and distribution -- Boilers, turbines, generators, transformers, power lines, nuclear reactors, oil wells, and pipelines. * Farming -- Tractors, combines, planters, etc. * Household conveniences -- Ovens, dish and clothes washers, vacuum cleaners, blenders, pumps, lawn mowers and trimmers, plumbing, water heaters, heating/cooling, etc. How are metals found in nature? Metals are an integral part of our planet and are found in almost all rocks and soils. Most metals form compounds, called minerals, which are naturally occurring, inorganic solids with regular chemical compositions and crystal structures. Although most metal-bearing mineral compositions comprise several elements, there are a few exceptions such as gold, which is found in its elemental form as a mineral called native gold. Metals can form, or be part of, many different minerals. The number of metals (over 70 in the periodic table) and their compounds results in an enormous array of minerals. Iron, for instance, which is very abundant in nature, is found in over 1100 minerals*. The brilliant colours frequently associated with gems such as emerald, ruby and sapphire reflect the variety of metal-containing minerals. Chalcopyrite, an important copper-bearing mineral, is bright yellow, while the copper-phosphate mineral, turquoise, has a blue colour. Minerals combine to become the rocks that make up our planet. Most rocks form considerably below the surface of the earth under the influence of pressure and heat. Geologic processes can cause them to move upward toward the surface. There, in the presence of oxygen and water, they break down, releasing elements - including metals - into solutions, and forming new minerals. This process, known as weathering, forms our soils. From soil, metals are taken up by plants and then by animals and humans in food. As soils are eroded, metal-bearing sediment is carried into streams and rivers, and eventually into the ocean. These sediments contribute to new rocks through ongoing geologic processes. Metals are ubiquitous in nature, and their distribution in the earth depends on geologic processes that have taken place. Some processes may form minerals with high metal contents; rocks containing these minerals may be so enriched that they can be mined at a profit - becoming ore deposits. Rocks that contain lower enrichments are known simply as mineral deposits. The metal content of deposits can range from a few parts per million (ppm) to as much as 650,000 ppm (65%) in the case of some iron ores. Mining companies employ special technologies to extract metals from complex ores in the production of pure metals such as iron, aluminum, copper and gold. While high concentrations of metals may lead to the formation of deposits, in many cases where the concentration of a metal is low, the metal may simply replace, or substitute for, another element in the crystal structure of common minerals. For example, rocks that make up the sea floor contain high concentrations of the metal magnesium, as well as smaller concentrations of nickel which substitute for some of the magnesium. Similarly, rocks that make up the continents can contain lead, which substitutes for the more abundant metallic element, potassium. This substitution phenomenon leads to the wide distribution of many metals at low concentrations throughout the rocks of the earth. Natural geologic processes continue at a very slow pace to concentrate and disperse metals, forming large zones of elevated metal concentrations and constantly releasing metals into the environment. A full understanding of these natural processes and the resulting metal dispersion patterns is important in the discovery and recovery of metals and for determining the impact of metals in the environment. What is a metal and what is a heavy metal? How many kinds of metals are there? What are the characteristics of metals? What are some applications of metals? What are the properties of metals? In what form are metals found? How are metals found in nature? Do we have adequate metals for the future? What are alloys? Which metals are essential for human health? Do deficiencies of essential trace elements cause any significant human health effects? Which metals are essential for plant health? Are Persistence, Bioaccumulation & Toxicity (PBT) appropriate criteria for ranking the hazards of inorganic metals and metal compounds? Are all metals in the soil and water bioavailable? What are the key steps in the health & ecological risk assessment of chemicals (including metals & metal compounds)? 1. Why did it take society so long to develop metals? 2. Define an alloy. 3. Why do metals break even though they are not stressed beyond their elastic limit? What conditions cause this type of failure? 4. What would be the advantage of alloys that would withstand higher temperatures? 5. Why does recycling save so much energy? 6. Removing elemental metal from its ore is called._______ 7. What impact does quenching have on ferrous metals? 8. What effect on tensile strength does stretching copper have? 9. Does rusting of steel occur at the anode of cathode? 10. What material is used as a "sacrificial" anode of steel? 11. What metal is alloyed with iron to make stainless steel? 12. What mechanical process is accomplished by stretching copper? 13. What happens to dislocations when a wire is bent? 14. Give the words for the following acronyms: FCC, BCC, HCP. 15. How does the metal composition differ in a paper clip and a bobby pin? 16. Compare the grain differences in normal steel and quenched steel. Answers to Review Questions 1. Why did it take society so long to develop metals. It is very difficult to form elemental metals from their ores. It often requires very high temperatures. The technology for this process took many years to develop. 2. Define an alloy. A substance that has metallic properties and is made up of two or more chemical elements, of which at least one is a metal. The two types of alloys are in 3. Why do metals break even though they are not stressed beyond their elastic limit? What conditions cause this type of failure? Under repetitive stresses, cracks in a metal can develop and grow. 4. What would be the advantage of alloys that would withstand higher temperatures? They could be used for many applications, such as higher temperature gasoline engines, nuclear reactor containment vessels, etc. 5. Why does recycling save so much energy? Because of the large amount of energy required to form elemental metals from their ores. 6. Removing elemental metal from its ore is called Extracting or Reduction . 7. What impact does quenching have on ferrous metals? If the metal contains carbon, the carbon will not be able to separate during the FCC to BCC transition and will be trapped, resulting in a distorted BCC structure. This hard, brittle form of steel is called Martensite. 8. What effect on tensile strength does stretching copper have? Stretching copper increases its tensile strength due to the formation of dislocations which become pinned. 9. Does rusting of steel occur at the anode of cathode? Rusting is an oxidation process and occurs at the anode. 10. What material is used as a "sacrificial" anode of steel? Zinc is used in galvanized steel. 11. What metal is alloyed with iron to make stainless steel? Chromium. 12. What mechanical process is accomplished by stretching copper? Cold-working. 13. What happens to dislocations when a wire is bent? More dislocations form and they get tangled or pinned. 14. Give the words for the following acronyms: FCC, BCC, HCP. FCC - Face centered cubic, BCC - Body centered cubic, HCP - hexagonal closest packed 15. How does the metal composition differ in a paper clip and a bobby pin? The bobby pin contains more carbon and is harder and stronger. 16. Compare the grain differences in normal steel and quenched steel. Normal steel contains separate grains of BCC arranged Fe and Fe3C. In quenched steel, the carbon remains in the BCC iron crystals distorting its structure. How are metals found in nature? Metals are an integral part of our planet and are found in almost all rocks and soils. Most metals form compounds, called minerals, which are naturally occurring, inorganic solids with regular chemical compositions and crystal structures. Although most metal-bearing mineral compositions comprise several elements, there are a few exceptions such as gold, which is found in its elemental form as a mineral called native gold. Metals can form, or be part of, many different minerals. The number of metals (over 70 in the periodic table) and their compounds results in an enormous array of minerals. Iron, for instance, which is very abundant in nature, is found in over 1100 minerals*. The brilliant colours frequently associated with gems such as emerald, ruby and sapphire reflect the variety of metal-containing minerals. Chalcopyrite, an important copper-bearing mineral, is bright yellow, while the copper-phosphate mineral, turquoise, has a blue colour. Minerals combine to become the rocks that make up our planet. Most rocks form considerably below the surface of the earth under the influence of pressure and heat. Geologic processes can cause them to move upward toward the surface. There, in the presence of oxygen and water, they break down, releasing elements - including metals - into solutions, and forming new minerals. This process, known as weathering, forms our soils. From soil, metals are taken up by plants and then by animals and humans in food. As soils are eroded, metal-bearing sediment is carried into streams and rivers, and eventually into the ocean. These sediments contribute to new rocks through ongoing geologic processes. Metals are ubiquitous in nature, and their distribution in the earth depends on geologic processes that have taken place. Some processes may form minerals with high metal contents; rocks containing these minerals may be so enriched that they can be mined at a profit - becoming ore deposits. Rocks that contain lower enrichments are known simply as mineral deposits. The metal content of deposits can range from a few parts per million (ppm) to as much as 650,000 ppm (65%) in the case of some iron ores. Mining companies employ special technologies to extract metals from complex ores in the production of pure metals such as iron, aluminum, copper and gold. While high concentrations of metals may lead to the formation of deposits, in many cases where the concentration of a metal is low, the metal may simply replace, or substitute for, another element in the crystal structure of common minerals. For example, rocks that make up the sea floor contain high concentrations of the metal magnesium, as well as smaller concentrations of nickel which substitute for some of the magnesium. Similarly, rocks that make up the continents can contain lead, which substitutes for the more abundant metallic element, potassium. This substitution phenomenon leads to the wide distribution of many metals at low concentrations throughout the rocks of the earth. Natural geologic processes continue at a very slow pace to concentrate and disperse metals, forming large zones of elevated metal concentrations and constantly releasing metals into the environment. A full understanding of these natural processes and the resulting metal dispersion patterns is important in the discovery and recovery of metals and for determining the impact of metals in the environment. Class A metals are metals that form hard acids. Hard acids are acids with relatively ionic bonds. These metals, such as iron, aluminum, titanium, sodium, calcium and the lanthanides, would rather bond with fluorine than iodine. They form stable products with hard bases, which are bases with ionic bonds. Class B metals are metals that form soft acids. Soft acids are acids with relatively covalent bonds. These metals, such as lead, gold, palladium, platinum, mercury and rhodium, would rather bond with iodine than fluorine. They form stable products with soft bases, which are bases with covalent bonds. Alkali metals Lithium, Sodium, Potassium Rubidium, Caesium, Francium Alkaline earth metals Beryllium, Magnesium, Calcium Strontium, Barium, Radium Transition metals Zinc, Molybdenum, Cadmium Scandium, Titanium, Vanadium Chromium, Manganese, Iron Cobalt, Nickel, Copper Yttrium, Zirconium, Niobium Technetium, Ruthenium, Rhodium Palladium, Silver, Hafnium Tantalum, Tungsten, Rhenium Osmium, Iridium, Platinum Gold, Mercury, Rutherfordium, Dubnium, Seaborgium, Bohrium, Hassium, Meitnerium, Darmstadtium, Roentgenium, Copernicium Post-transition metals Aluminium, Gallium, Indium Tin, Thallium, Lead, Bismuth Ununtrium, Ununquadium Ununpentium, Ununhexium Lanthanoids Lanthanum, Cerium, Praseodymium Neodymium, Promethium, Samarium Europium, Gadolinium, Terbium Dysprosium, Holmium, Erbium Thulium, Ytterbium, Lutetium Actinoids Actinium, Thorium, Protactinium Uranium, Neptunium, Plutonium Americium, Curium, Berkelium Californium, Einsteinium, Fermium Mendelevium, Nobelium, Lawrencium General Questions 1 What is an Ore? 2 What is the Difference between an Ore and a Mineral? 3 What are the most common Metal Ores? 4 Are Ores a Finite Resource? 5 Are Ores Renewable? 6 Name a Source of Metals other than Ores? 7 When is Carbon used for Extraction? 8 When is Electrolysis used for Extraction? 9 What does Native Metal mean? 10 What was the first really Useful Metal? Electrolysis of Lead Bromide 11 Why is Lead Bromide Heated until it is Molten? 12 What are the Equations at the Electrodes called? 13 Do Lead Ions Gain or Lose Electrons at the Cathode? 14 Is the reaction at the Cathode called Oxidation or Reduction? 15 Write the Balanced Equation for the Overall Reaction. Extraction of Aluminium 16 What is Aluminium Ore called? 17 What is the Chemical Formula for Aluminium Oxide? 18 Why is Cryolite added to Aluminium Ore? 19 Which Gases are given off at the Anode? 20 Why does the Anode need to be Replaced? 21 Write the Balanced Equation for the Overall Reaction. 22 Why is Aluminium More Expensive than Iron? 23 Why is Aluminium Resistant to Corrosion? 24 What is Anodising? 25 What Substance is used to Remove the Oxide Layer before Anodising? 26 Which Acid is used as the Electrolyte for Anodising? 27 Which Gas is given off at the Anode during Anodising? 28 Which Gas is given off at the Cathode during Anodising? 29 Does Aluminium have a High Density? 30 Is Aluminium a Good Conductor of Heat? 31 Give two uses of Aluminium. Extraction of Iron 32 What is Haematite? 33 Which three Raw Materials are added through the Top of the Blast Furnace? 34 What is Coke? 35 Write the Balanced Equation for the Combustion of Coke. 36 Which compound Reduces Iron in the Blast Furnace? 37 Write the Balanced Equation for the Reduction of Iron in the Blast Furnace. 38 Why is Limestone used in the Blast Furnace? 39 What is Thermal Decomposition of Limestone. 40 Write the Balanced Equation for the Thermal Decomposition of Limestone. 41 Give one Use of Slag. 42 Where does the Carbon in Cast Iron come from? 43 How can the amount of Carbon in Cast Iron be Reduced? 44 Which Alloy is the majority of Iron made into? 45 Is Iron a Magnetic Metal? 46 Is Cast Iron brittle? 47 Does Cast Iron Rust more easily than Steel? 48 Give one Use of Cast Iron. 49 Give one Use of Wrought Iron. Purification of Copper 50 Is the Anode made from Pure or Impure Copper? 51 Which Compound is used as the Electrolyte during Purification? 52 Write the equation for the Reduction of Copper at the Cathode. 53 Is Copper a Magnetic Metal? 54 Is Copper a Good Conductor of Electricity? 55 Is Copper Resistant to Corrosion? 56 Give two Uses of Copper. Extraction of Titanium 57 What is Rutile? 58 Which Compound of Titanium does Rutile contain? 59 Why is Titanium not Extracted by Electrolysis? 60 Write the Equation for the Reaction of Magnesium with Titanium Chloride. 61 Why does the Reaction need an Argon Atmosphere? 62 Does Titanium have a High Density? 63 Is Titanium Hard? 64 Is Titanium Resistant to Corrosion? 65 Give one Use of Titanium Alloys. Alloys 66 What is an Alloy? 67 How can Adding Metals change the Properties of an Alloy? 68 What is Duralumin? 69 What is Brass? 70 Give one Use of Brass. 71 What is Bronze? 72 Give one Use of Bronze. 73 Give one Use of Cupro-nickel. 74 What is Steel? 75 Is Low Carbon Steel used to make Bridges? 76 Is Low Carbon Steel used to make Tools? 77 What is Manganese Steel used for? 78 What is Stainless Steel used for? 79 What is Rusting? 80 How is Rusting prevented? Give two methods. 81 What is Zinc Plating called? 82 What Electrolyte would you use for Silver Plating? 83 What is Sacrificial Protection of Iron or Steel? 84 When is Sacrificial Protection used? 85 What is Solder? 86 Give one Use of Solder. 87 Give one use of Titanium. 33 Which three Raw Materials are added through the Top of the Blast Furnace? Iron ore, coke and limestone Iron is extracted from its ore in the blast furnace. The main iron ore is called haematite. Haematite is iron(III) oxide - Fe2O3. The iron ore contains impurities, mainly silica (silicon dioxide). Limestone (calcium carbonate) is added to the iron ore which reacts with the silica to form molten calcium silicate in the blast furnace. The calcium silicate (called slag) floats on the liquid iron. Since iron is below carbon in the reactivity series, iron in the ore is reduced to iron metal by heating with carbon (coke). It is actually carbon monoxide which does the reducing in the blast furnace. Hot air is blasted into the furnace causing coke (carbon) to burn rapidly and raise the temperature to 2000 �C. The carbon dioxide then reacts with hot carbon to form carbon monoxide. Carbon monoxide then reduces iron in the ore to iron metal. The temperature where the reduction takes place is above 1500 �C. Iron falls to the bottom of the furnace where the temperature is 2000 �C. Iron is liquid at this temperature and is tapped off periodically. What is a metal and what is a heavy metal? How many kinds of metals are there? What are the characteristics of metals? How are metals found in nature? What are some applications of metals? * What are the properties of metals? * In what form are metals found? * How are metals found in nature? * Do we have adequate metals for the future? * What are alloys? * Which metals are essential for human health? * Do deficiencies of essential trace elements cause any significant human health effects? * Which metals are essential for plant health? * Are Persistence, Bioaccumulation & Toxicity (PBT) appropriate criteria for ranking the hazards of inorganic metals and metal compounds? * Are all metals in the soil and water bioavailable? * What are the key steps in the health & ecological risk assessment of chemicals (including metals & metal compounds)? 1. Why did it take society so long to develop metals? 2. Define an alloy. 3. Why do metals break even though they are not stressed beyond their elastic limit? What conditions cause this type of failure? 4. What would be the advantage of alloys that would withstand higher temperatures? 5. Why does recycling save so much energy? 6. Removing elemental metal from its ore is called._______ 7. What impact does quenching have on ferrous metals? 8. What effect on tensile strength does stretching copper have? 9. Does rusting of steel occur at the anode of cathode? 10. What material is used as a "sacrificial" anode of steel? 11. What metal is alloyed with iron to make stainless steel? 12. What mechanical process is accomplished by stretching copper? 13. What happens to dislocations when a wire is bent? 14. Give the words for the following acronyms: FCC, BCC, HCP. 15. How does the metal composition differ in a paper clip and a bobby pin? 16. Compare the grain differences in normal steel and quenched steel. Answers to Review Questions 1. Why did it take society so long to develop metals. It is very difficult to form elemental metals from their ores. It often requires very high temperatures. The technology for this process took many years to develop. 2. Define an alloy. A substance that has metallic properties and is made up of two or more chemical elements, of which at least one is a metal. 3. Why do metals break even though they are not stressed beyond their elastic limit? What conditions cause this type of failure? Under repetitive stresses, cracks in a metal can develop and grow. 4. What would be the advantage of alloys that would withstand higher temperatures? They could be used for many applications, such as higher temperature gasoline engines, nuclear reactor containment vessels, etc. 5. Why does recycling save so much energy? Because of the large amount of energy required to form elemental metals from their ores. 6. Removing elemental metal from its ore is called Extracting or Reduction . 7. What impact does quenching have on ferrous metals? If the metal contains carbon, the carbon will not be able to separate during the FCC to BCC transition and will be trapped, resulting in a distorted BCC structure. This hard, brittle form of steel is called Martensite. 8. What effect on tensile strength does stretching copper have? Stretching copper increases its tensile strength due to the formation of dislocations which become pinned. 9. Does rusting of steel occur at the anode of cathode? Rusting is an oxidation process and occurs at the anode. 10. What material is used as a "sacrificial" anode of steel? Zinc is used in galvanized steel. 11. What metal is alloyed with iron to make stainless steel? Chromium. 12. What mechanical process is accomplished by stretching copper? Cold-working. 13. What happens to dislocations when a wire is bent? More dislocations form and they get tangled or pinned. 14. Give the words for the following acronyms: FCC, BCC, HCP. FCC - Face centered cubic, BCC - Body centered cubic, HCP - hexagonal closest packed V 15. How does the metal composition differ in a paper clip and a bobby pin? The bobby pin contains more carbon and is harder and stronger. 16. Compare the grain differences in normal steel and quenched steel. Normal steel contains separate grains of BCC arranged Fe and Fe3C. In quenched steel, the carbon remains in the BCC iron crystals distorting its structure. How are metals found in nature? Metals are an integral part of our planet and are found in almost all rocks and soils. Most metals form compounds, called minerals, which are naturally occurring, inorganic solids with regular chemical compositions and crystal structures. Although most metal-bearing mineral compositions comprise several elements, there are a few exceptions such as gold, which is found in its elemental form as a mineral called native gold. Metals can form, or be part of, many different minerals. The number of metals (over 70 in the periodic table) and their compounds results in an enormous array of minerals. Iron, for instance, which is very abundant in nature, is found in over 1100 minerals*. The brilliant colours frequently associated with gems such as emerald, ruby and sapphire reflect the variety of metal-containing minerals. Chalcopyrite, an important copper-bearing mineral, is bright yellow, while the copper-phosphate mineral, turquoise, has a blue colour. Minerals combine to become the rocks that make up our planet. Most rocks form considerably below the surface of the earth under the influence of pressure and heat. Geologic processes can cause them to move upward toward the surface. There, in the presence of oxygen and water, they break down, releasing elements - including metals - into solutions, and forming new minerals. This process, known as weathering, forms our soils. From soil, metals are taken up by plants and then by animals and humans in food. As soils are eroded, metal-bearing sediment is carried into streams and rivers, and eventually into the ocean. These sediments contribute to new rocks through ongoing geologic processes. Metals are ubiquitous in nature, and their distribution in the earth depends on geologic processes that have taken place. Some processes may form minerals with high metal contents; rocks containing these minerals may be so enriched that they can be mined at a profit - becoming ore deposits. Rocks that contain lower enrichments are known simply as mineral deposits. The metal content of deposits can range from a few parts per million (ppm) to as much as 650,000 ppm (65%) in the case of some iron ores. Mining companies employ special technologies to extract metals from complex ores in the production of pure metals such as iron, aluminum, copper and gold. While high concentrations of metals may lead to the formation of deposits, in many cases where the concentration of a metal is low, the metal may simply replace, or substitute for, another element in the crystal structure of common minerals. For example, rocks that make up the sea floor contain high concentrations of the metal magnesium, as well as smaller concentrations of nickel which substitute for some of the magnesium. Similarly, rocks that make up the continents can contain lead, which substitutes for the more abundant metallic element, potassium. This substitution phenomenon leads to the wide distribution of many metals at low concentrations throughout the rocks of the earth. Natural geologic processes continue at a very slow pace to concentrate and disperse metals, forming large zones of elevated metal concentrations and constantly releasing metals into the environment. A full understanding of these natural processes and the resulting metal dispersion patterns is important in the discovery and recovery of metals and for determining the impact of metals in the environment. |