Strong under tension and compression. Malleable. Low density. Have a dull appearance. Good conductors of electricity and heat

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1 Revision from Year 10: Properties of Metals and Non-Metals Read CC pp Use arrows to link the properties with the materials: Strong under tension and compression Malleable Low density Have a dull appearance Good conductors of electricity and heat Can form negative ions when they react Brittle Metals Shiny when polished Sonorous Usually form acidic oxides with oxygen Poor conductors of electricity and heat High density Low melting and boiling points Usually form basic oxides with oxygen Usually form positive ions when they react Ductile Non-Metals All of the above are physical properties apart from 4 (2 for metal and 2 for non-metals). Highlight and label the chemical properties. Give equations below to show the chemical properties for metals:

2 Reactivity of metals We can deduce how reactive a metal is by observing how it reacts with other elements and compounds. We need to be able to use the reactions of a metal with water and dilute acid to determine its reactivity. With water... Metal: Reaction: Order of reactivity: Potassium Sodium* Violent reaction with cold water. Floats and catches fire. Very vigorous reaction with cold water. Floats. Can be lit with a lighted splint. Write the reactions for the metals with an asterisk: Products: 1 st Potassium hydroxide, KOH and hydrogen gas. 2nd. Sodium hydroxide, NaOH and hydrogen gas. Calcium Less vigorous with cold water. 3rd. Calcium hydroxide, Ca(OH)2 and hydrogen gas. Magnesium Very slow with cold water, but vigorous with steam. 4th. Magnesium oxide, MgO and hydrogen gas. Zinc* Quite slow with steam. 5th. Zinc oxide, ZnO and hydrogen gas. Iron* Slow with steam. 6th. Iron oxide, Fe203 and hydrogen gas. Copper No reaction with steam. 7 th

3 With dilute hydrochloric acid... Metal: Reaction with hydrochloric acid: Magnesium* Vigorously reacts with a stream of gas evolving. Zinc* Iron Lead* Quite slow reaction with a steady stream of gas evolving. Slow reaction with a gentle stream of gas evolving. Very slow and acid must be concentrated. NB. More reactive metals react with acid explosively. Again, write the reactions for the indicated metals: Order of Products: reactivity: 1 st Magnesium chloride, MgCl2 and hydrogen gas. 2nd. Copper No reaction. 5 th 3rd. 4th. Zinc chloride, ZnCl2 and hydrogen gas. Iron chloride, FeCl2 and hydrogen gas. Lead chloride, PbCl2 and hydrogen gas. Notes: 1. Aluminium is a reactive metal, but does not appear to be in its reaction with water and dilutes acids. Why? 2. Sulphuric acid reacts in a similar way to hydrochloric acid, apart from with Calcium. Why? EXPT: Metals and Acids

4 The reactivity series Metals above carbon cannot be extracted by reduction of their oxides by carbon or carbon monoxide Metals above hydrogen will react with acids to produce hydrogen gas Notes: 1. Metals above carbon in the list must be extracted using electrolysis. 2. The reactivity of a metal is a measure of how easily the metal loses electrons to form positive ions. eg. Potassium loses its valence electron very easily and is very reactive. Ionic Copper resists losing its electrons and is relatively unreactive. Ionic 3. A consequence of this is that reactive metals for very stable compounds - it is hard to make them form atoms again. CC p184 Q1-4

5 #Breaking down using heat Thermal decomposition# of metal carbonates, hydroxides and nitrates Compounds of Sodium and Potassium resist thermal decomposition as they are very stable. The general rules are as follows: Do not decompose Do decompose Carbonates K, Na All other metals - to give the oxide and carbon dioxide* Hydroxides K,Na All other metals - to give the oxide and water* Nitrates Na and K give the nitrite and oxygen* Other metals give the oxide, nitrogen dioxide and oxygen* Give an equation for the thermal decomposition of: Zinc Carbonate Calcium Hydroxide Sodium Nitrate Magnesium Nitrate Demo: The above reactions

6 Competition for Oxygen A more reactive metal will displace a less reactive metal from its oxide in an attempt to form a more stable oxide. Eg1. Iron and Copper(II)Oxide Oxidation half equation: Reduction half equation: Eg2. Demo: Zinc and Copper(II)Oxide Half equations: Oxidation: Reduction: Eg3: The Thermit Process Aluminium with Iron(III)Oxide H is VERY negative In all of the above reactions, heat is needed to start the reaction, then the large amount of heat that the reaction produces makes the reaction proceed rapidly. The thermite process produces so much heat energy that molten iron is made, which can be used to repair railway tracks in situ. Chemistry sometimes goes wrong... Displacement reactions in solution

7 Any more reactive metal will displace a less reactive metal from a solution of one of its salts. Demo: Zinc and Copper Sulphate solution Ionic Observations: The reactive metal is acting as a REDUCING agent. CC p187 Q1-6 AV - Reactivity Expt: Competition between metals Revision from Year 10: Simple Cells Remember, placing 2 different metals in an electrolyte and making a circuit will cause an electric current to flow. The greater the difference in reactivity of the 2 metals, the greater the voltage produced. Note: the more reactive metal pole, and the less reactive the positive pole. is called the negative Exam Questions: CC p

8 10.3(a) Extraction of Metals Read CC pp The extraction of a metal from its ore always involves the reduction of the metal. General The method of extraction depends on the reactivity of the metal. The more reactive the metal, the harder it is to extract. examples: Some specific 1. Copper CHALCOPYRITE (mainly copper(ii)sulphide) is roasted in air to give the metal and sulphur dioxide:

9 2. Zinc ZINC BLENDE (mainly zinc sulphide) is roasted in air to produce zinc oxide: This oxide is then reduced with carbon monoxide (the reducing agent): Iron is produced in a similar way (see below). DEMO: Lead from lead oxide 3. Aluminium (revision of Year 10) Alumina is reduced using electrolysis, due to the fact that Aluminium is a more reactive metal: NB. The oxygen produced at the graphite ANODE reacts to give carbon dioxide and forces the periodic replacement of this electrode.

10 The Blast Furnace The charge is the mixture of Haematite (Iron(III)Oxide), Limestone (Calcium Carbonate) and Coke (produced by heating coal in the absence of air). You must learn the following BIG 5 EQUATIONS 1. Coke burns with oxygen in a very exothermic reaction (which heats the blast furnace): 2. The limestone thermally decomposes: 3. The carbon dioxide from reactions 1 and 2 reacts with more coke to produce the reducing agent (carbon monoxide): 4. The Haematite is reduced: The molten iron collects at the bottom of the furnace. 5. The calcium Oxide produced in reaction 2 reacts with impurities (mainly silicon(iv)oxide) to produce silicates. This material is commonly known as slag and is used for foundations for buildings and for making roads. The molten slag floats on the iron and is periodically removed.

11 Turning Cast Iron into Steel The iron drained from the blast furnace contains a high percentage of carbon (4%) and some impurities. This is called cast iron or pig iron. The high percentage of carbon makes it HARD and BRITTLE, and it is used for manhole covers, gates, fences, etc where strength is not important. NB. Steel is an alloy of iron mixed with small amounts of carbon and other metals. The process of making steel is: 1. Molten cast iron is poured into an oxygen furnace. 2. Scrap iron is added.* 3. Calcium oxide is added to remove impurities as slag: 4. Oxygen is bubbled through the molten iron to remove the percentage of carbon (detectors control the carbon content). 5. Other metals are added according to the alloy being made. *This is how iron and steel are recycled. They can be separated from waste metals in scrapyards using an electromagnet and thrown into the oxygen furnace to be reused. CC p199 Q1-5

12 Why make alloys? Key concept: Uses depend on properties. Adding a small amount of another metal (or carbon/silicon) to a pure metal can really changes its properties, eg. malleability, ductility, strength, electrical conductivity, melting point, etc. We can see why by considering the structure of an alloy. Diagram: Consider the alloys of iron: Type of steel Iron alloyed with Properties Typical use low carbon steel Mild Steel about 0.25 percent carbon easily shaped car body panels high carbon steel up to 2.5 percent carbon hard cutting tools stainless steel chromium and nickel resistant to corrosion cutlery, sinks, chemical plants,...

13 Aluminium CC pp Fill in the following tables: Uses and properties of pure aluminium (Year10) Use Related properties Constitution, uses and properties of the Aluminium alloy Duralumin (7075TF) Made from... Use Related properties Copper Fill in the following tables: Uses and properties of pure copper Use Related properties Constitution, uses and properties of brass (one of copper s alloys): Made from... Use Related properties Zinc Uses and properties of pure zinc (as well as for making brass!): Use Related properties

14 ! Task: Recycling metals Using the internet, investigate the advantages and disadvantages of recycling iron/steel and aluminium and construct a table listing them. Exam Questions: CC pp Exam Questions

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