Iron(Metal)man. Properties of Metal. Structure of Metals. Learning Objectives. Physical properties of metals. Physical properties VS structure

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Shon Chambers
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Iron(Metal)man Properties of Metal Why does Ironman appear to be shiny all over? Why is it possible for Ironman to use metal as his costume? Why does Ironman not get hurt easily? Will he melt easily?

1 Iron(Metal)man Properties of Metal Why does Ironman appear to be shiny all over? Why is it possible for Ironman to use metal as his costume? Why does Ironman not get hurt easily? Will he melt easily? Does he get burnt easily? created by Janelle Tay (2010) 1 created by Janelle Tay (2010) 2 Learning Objectives Structure of Metals 1. Describe the general properties of metals with respect to its structure. The atoms are of the same sizes. created by Janelle Tay (2010) 3 created by Janelle Tay (2010) 4 Physical properties of metals Solid at room temperature High density High melting and boiling points Malleable Ductile Good conductor of electricity and heat Physical properties of any substances are determined by the way its particles are packed Atoms in a metal are packed regularly in layers Held together by strong metallic bond Metals have high densities, melting points and boiling points created by Janelle Tay (2010) 5 created by Janelle Tay (2010) 6 1

Physical Property How is it related to the structure? High density Giant metallic structure Atoms arranged in a regular and closely packed manner Physical Property How is it related to the structure?

2 Physical Property How is it related to the structure? High density Giant metallic structure Atoms arranged in a regular and closely packed manner Physical Property How is it related to the structure? High melting and boiling points Atoms are held together by strong metallic bonds. A lot of energy is required to break apart the strong metallic bonds in the giant lattice created by Janelle Tay (2010) 7 created by Janelle Tay (2010) 8 Physical Property Explanation Ductile and malleable Atoms of the same size makes it easy for layers of atoms to slide over each other when force is applied Physical Property High thermal and electrical conductivity Explanation Atoms are tightly packed but the outermost electrons of the atoms break away easily from the atoms Positive (metal) ions are surrounded by the sea of mobile electrons The mobile electrons allow metals to conduct electricity. Heat is also transferred easily by the mobile electrons in the structure. created by Janelle Tay (2010) 9 created by Janelle Tay (2010) 10 Sea of mobile electrons **NOTE: NOT all metals obey all the above physical properties mentioned. HOWEVER, ALL metals conduct electricity and this fact distinguish a metal from a non-metal. Animation of sea of mobile electrons created by Janelle Tay (2010) 11 created by Janelle Tay (2010) 12 2

Pure metals Useful properties but not widely used This is because many pure metals are soft corrode easily (may react with air and water and wear away easily).

Identify representations of metals and alloys from diagrams of structures. 3. Explain why alloys are stronger than pure metals.

3 Pure metals Useful properties but not widely used This is because many pure metals are soft corrode easily (may react with air and water and wear away easily). Most metallic substances used nowadays are ALLOYS! created by Janelle Tay (2010) 13 created by Janelle Tay (2010) 14 Learning Objectives 1. Define what an alloy is and give examples of alloys. 2. Identify representations of metals and alloys from diagrams of structures. 3. Explain why alloys are stronger than pure metals. created by Janelle Tay (2010) 15 created by Janelle Tay (2010) 16 An alloy is a mixture of a metal with one or a few other elements. Name of alloy Bronze Composition Copper and tin Metals VS alloys Pure Metals 1. Soft and weak 1. Hard and strong 2. Easily corroded 2. Corrosion-resistant 3. Loses metallic shine easily 3. Metallic shine is preserved Stainless steel Iron, chromium, nickel and carbon created by Janelle Tay (2010) 17 created by Janelle Tay (2010) 18 3

Structure: Structure of metals and alloys Atoms in pure metals are closely packed and regularly arranged. With force, the layers of atoms slide over each other, making the metal weak.

Disrupts the orderly arrangement of the atoms of the pure metal Makes it more difficult for the atoms to slide over each other Makes the alloy stronger, harder and less malleable Foreign atom created

4 Structure: Structure of metals and alloys Atoms in pure metals are closely packed and regularly arranged. With force, the layers of atoms slide over each other, making the metal weak. This explains why metals are malleable and ductile. Structure of metals and alloys Structure: In an alloy, a foreign atom of another element is added into the pure metal. Disrupts the orderly arrangement of the atoms of the pure metal Makes it more difficult for the atoms to slide over each other Makes the alloy stronger, harder and less malleable Foreign atom created by Janelle Tay (2010) 19 created by Janelle Tay (2010) 20 Hard and strong, less malleable Improves appearance of the pure metal Pewter (alloy of tin, antimony and copper) is used to make ornaments and souvenirs as it looks more attractive than pure tin More resistant to corrosion E.g. Copper corrodes easily so an alloy of copper is used to make coins Lower the melting point of metals E.g. Solder (an alloy of tin and lead) has lower melting point hence is used to join metals created by Janelle Tay (2010) 21 created by Janelle Tay (2010) 22 Use of alloys Pure metals Metals Alloy Mixture of Uses Special properties Brass Copper and zinc Electricplug, coins, musical instruments Stainless steel Pewter Iron, chromium and nickel Lead, tin, some antimony Does not corrode easily, attractive yellow colour like gold Cutlery, utensils, Resistant to corrosion medical instruments Souvenirs, ornaments Bright, shiny colour like silver Solder Tin and lead Joining metals Lowmelting point Bronze Copper and tin Propellers, ornaments Less brittle, corrosion resistant Physical Properties High density High melting and boiling points Malleable Physical properties Lower melting point Hard, strong and less malleable Resistant to corrosion created by Janelle Tay (2010) 23 Ductile Good conductor of electricity and heat Mixture of a metal with one or a few other elements Made by mixing the molten elements (metals or metal and carbon) in the right proportions and allowing them to created solidify by Janelle Tay (2010) 24 4

5 Exercise a(i) A positive ion, Mg 2+, is formed when Mg atom loses 2 valence electrons. Hence, the structure of magnesium metal consists of positive magnesium ions in a sea of mobile electrons. These mobile electrons carry electric charges throughout the metal structure, therefore, conducting electricity. Exercise a(ii) The structure of magnesium consists of atoms arranged in an orderly manner and are closely packed. When a force is applied, the layers of atoms can slide over each other easily. Therefore, it is malleable (can be beaten into thin sheets). created by Janelle Tay (2010) 25 created by Janelle Tay (2010) 26 5

Ionic and Metallic Bonding

Ionic and Metallic Bonding BNDING AND INTERACTINS 71 Ions For students using the Foundation edition, assign problems 1, 3 5, 7 12, 14, 15, 18 20 Essential Understanding Ions form when atoms gain or lose