Properties of Metals
Section: 9. Metals | Syllabus: Cambridge AS Level Physics 9702
What are Metals? Metals are elements that typically have characteristic physical and chemical properties. Most elements in the Periodic Table are metals - they are found on the left and center of the Periodic Table.
Examples of common metals: Group 1: Lithium (Li), Sodium (Na), Potassium (K) Group 2: Magnesium (Mg), Calcium (Ca) Transition metals: Iron (Fe), Copper (Cu), Zinc (Zn), Gold (Au), Silver (Ag) Group 13: Aluminum (Al) Physical Properties of Metals Metals share several characteristic physical properties: 1.
High Melting and Boiling Points Most metals have high melting points They are solid at room temperature (except mercury, which is liquid) Due to strong metallic bonding between atoms Metal Melting Point (°C) Iron (Fe) 1538 Copper (Cu) 1085 Aluminum (Al) 660 Zinc (Zn) 420 Sodium (Na) 98 Mercury (Hg) -39 (liquid at room temp) Exception Mercury is the only metal that is liquid at room temperature.
Group 1 metals have relatively low melting points for metals. 2. Good Conductors of Heat Metals conduct heat efficiently Heat energy passes quickly through metals Free (delocalized) electrons transfer kinetic energy Examples of use: Cooking pots and pans (copper, aluminum, steel) Radiators and heat exchangers Cooling fins on electronic devices 3.
Good Conductors of Electricity Metals are excellent electrical conductors Free electrons move through the metal structure Can carry electric current with low resistance Best conductors (in order): Silver (Ag) - best conductor, but expensive Copper (Cu) - commonly used in wires Gold (Au) - used in electronics (doesn't corrode) Aluminum (Al) - used in overhead power cables 4.
Malleable Malleability is the ability to be hammered or pressed into different shapes without breaking. Metals can be beaten into thin sheets Layers of atoms can slide over each other Metallic bonds remain intact during deformation Examples: Gold can be beaten into extremely thin gold leaf Aluminum is rolled into foil for food packaging Steel is shaped into car body panels 5.
Ductile Ductility is the ability to be drawn out into wires. Metals can be stretched into thin wires Atoms slide past each other without breaking bonds Important for making electrical cables Examples: Copper drawn into electrical wires Steel drawn into cables and springs Tungsten drawn into light bulb filaments 6.
High Density Most metals have high density Atoms are closely packed together Metals feel heavy for their size Metal Density (g/cm³) Gold (Au) 19.3 Lead (Pb) 11.3 Copper (Cu) 8.9 Iron (Fe) 7.9 Aluminum (Al) 2.7 (low for a metal) 7.
Metallic Luster (Shiny) Metals have a characteristic shiny appearance They reflect light well Surface must be clean (not oxidized) to be shiny Examples: Silver and gold used in jewelry (highly reflective) Aluminum used in mirrors and reflectors Chrome plating for decorative shine 8.
Strong and Hard Most metals are strong (resist forces) Most metals are hard (resist scratching) Due to strong metallic bonding Exceptions Group 1 metals (Na, K) are soft enough to be cut with a knife.
This is because they have only one electron contributing to metallic bonding. 9. Produce a Ringing Sound (Sonorous) Metals make a ringing sound when struck Called being "sonorous" Vibrations travel well through metal structure Examples: Bells made from bronze or steel Cymbals made from brass Tuning forks made from steel Chemical Properties of Metals 1.
Reaction with Oxygen Most metals react with oxygen to form metal oxides: General equation: Metal + Oxygen → Metal Oxide Examples: 2Mg(s) + O₂(g) → 2MgO(s) magnesium + oxygen → magnesium oxide (white powder) 4Fe(s) + 3O₂(g) → 2Fe₂O₃(s) iron + oxygen → iron(III) oxide (rust) Metal oxides are basic Reactive metals burn brightly in oxygen Less reactive metals corrode slowly 2.
Reaction with Water Reactive metals react with water to form metal hydroxide and hydrogen gas: General equation: Metal + Water → Metal Hydroxide + Hydrogen Example: 2Na(s) + 2H₂O(l) → 2NaOH(aq) + H₂(g) sodium + water → sodium hydroxide + hydrogen Group 1 metals (Na, K) react vigorously with cold water Calcium reacts moderately with cold water Magnesium reacts slowly with cold water, faster with steam Less reactive metals (Cu, Au, Ag) do NOT react with water 3.
Reaction with Acids Metals above hydrogen in the reactivity series react with dilute acids: General equation: Metal + Acid → Salt + Hydrogen Example: Zn(s) + H₂SO₄(aq) → ZnSO₄(aq) + H₂(g) zinc + sulfuric acid → zinc sulfate + hydrogen Reactive metals react vigorously (fizzing, heat) Hydrogen gas is produced (pop test) Metals below hydrogen (Cu, Ag, Au) do NOT react 4.
Formation of Positive Ions Metals lose electrons to form positive ions (cations) This is called oxidation Metals are reducing agents Examples: Na → Na⁺ + e⁻ Mg → Mg²⁺ + 2e⁻ Al → Al³⁺ + 3e⁻ Summary: Physical Properties of Metals Property Description Reason High melting point Usually solid at room temperature Strong metallic bonds Electrical conductivity Conduct electricit…
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