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Non-Metals. Prepared December 2007 Alrick Moodie. What are non-metals ?. Non-metals are those substances which are not metals i.e. they do not ionize by electron loss and do not show the characteristics of metals. Properties of Non-Metals. Poor conductors of heat and electricity
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Non-Metals Prepared December 2007 Alrick Moodie
What are non-metals ? • Non-metals are those substances which are not metals i.e. they do not ionize by electron loss and do not show the characteristics of metals
Properties of Non-Metals • Poor conductors of heat and electricity • Brittle , not malleable and ductile • Dull in colour • Low in sonority
Chemical Properties • React with air/oxygen to give covalent acidic oxides ( although a few give neutral oxides e.g. CO ) • React with metals to form ionic compounds • Do not react with dilute acids • Do not react with water except chlorine • Tend to be oxidizing agents
Common Non-metals We will be looking at : • Hydrogen • Chlorine • Oxygen • Carbon • Sulphur • Nitrogen
Hydrogen It is a diatomic gas H2 It is colourless and odourless . It is almost insoluble in water and is the lightest known substance .
Chemical Properties of Hydrogen • It has a neutral pH • It burns in air/oxygen • It combines with reactive metals to give hydrides : Mg + H2 MgH2 • It can act as a reducing agents e.g. in the extraction of metals CuO + H2 Cu + H2O
Uses of Hydrogen • Manufacture of ammonia , nitric acid and nylon • Manufacture of margarine and other hydrogenated oils • In welding • As fuel
Laboratory Preparation • Hydrogen can be prepared by reacting an acid with a metal Zn + 2HCl ZnCl2 + H2
Water vapour in the atmosphere condenses and form water droplets and precipitation occurs . If temperature is low we will get snow or hail ( ice ) . The water on the ground : • percolates and go underground • runs off into rivers and the seas • evaporates
Plants absorb water and loses it through a process called transpiration Animals also intake water and lose through excretion ( sweat , urine or breathing )
Uses of water • Domestic purposes e.g. drinking , washing , cooking , cleaning • Irrigation of crops • Generation of electricity • Industrial processes • Recreational activities
Chlorine It is a diatomic gas Cl2 It is a greenish-yellow gas with a choking odour . It is more dense than air and is slightly soluble in water .
Chemical Properties of Chlorine • Readily combines with metals to form chlorides : Mg + Cl2 MgCl2 • It is a powerful oxidizing agent • It bleaches substances ( in the presence of moisture )
Uses of Chlorine • Manufacture of plastics e.g. PVC • Sterilize water e.g. drinking supplies , swimming pools • Preparation of cleaning fluids and bleaching agents • Manufacture of hydrochloric acid
Laboratory Preparation • Chlorine can be the oxidation of conc. Hydrochloric acid by potassium manganate VII HCl (l) + KMnO4(s) KCl (aq) + MnCl2 (aq) + H2O (l) + Cl2 (g)
Oxygen is the most abundant element on Earth . Approximately 50% of the earth’s crust is composed of oxygen containing compounds , while 20% of the atmosphere is free oxygen gas .
Oxygen is a diatomic gas O2 although in the upper atmosphere it exists in the allotrope form as ozone O3 . It is a colourless odourless gas which is slightly soluble in water and has the same density as air .
Chemical Properties • It has a neutral pH of 7 • Supports combustion • Combines with most elements to form oxides • It is involved in biological processes of respiration .
Uses of Oxygen • In welding apparatus • Rocket fuels • Steel manufacture • Breathing equipment
Laboratory Preparation Oxygen is prepared by the catalytic decomposition of hydrogen peroxide . 2H2O2 (aq) 2H2O (l) + O2 (g) MnO2 is the catalyst used
Carbon exists as many natural occurring allotropes ; diamond , graphite , charcoal and coke .
Chemical Properties of Carbon • Readily burns in oxygen to form carbon dioxide . In limited supply of air carbon monoxide is formed . • It is a powerful reducing agent at high temperatures .
Carbon Dioxide Carbon dioxide is a colourless , odourless gas which is slightly soluble in water . It is more dense than air and is slightly acidic . The presence of carbon dioxide can be determined by the formation of a precipitate with calcium hydroxide .
Preparation Carbon dioxide is prepared by the reaction of a carbonate and a dilute acid .
Uses of Carbon dioxide • As a refrigerant • As a fire suppressant • In sodas
Sulphur is found in the earth’s crust as a free element and as sulphides and sulphates . The free sulphur occurs as two allotropes , monoclinic and rhombic .
Chemical Properties • Burns in air to form sulphur dioxide • Combines with most metals to form sulphides .
Uses • Manufacture of sulphuric acid • Manufacture of gunpowder and matches • Manufacture of fungicides and pesticides • Vulcanization of rubber
Sulphur is obtained by the Frasch process where the sulphur is mined directly from the earth in its elemental form .
Concentrated sulphuric acid is a colourless , odourless , oily liquid . It is a powerful dehydrating liquid . Diluting conc. sulphuric acid is a very exothermic reaction and must be done cautiously .
Uses • Manufacture of fertilizers • Manufacture of white paint • Manufacture of soaps and detergents • Refining of petroleum • Vulcanization
Manufacture Sulphuric acid is manufactured by the Contact process which has three stages . • Sulphur is burned in air to form sulphur dioxide S (s) + O2 (g) SO2 (g) • The sulphur dioxide is oxidized to sulphur trioxide 2SO2 (g) + O2 (g) 2SO3 (g)
The sulphur trioxide is dissolved in concentrated sulphuric acid to form oleum which is diluted to form sulphuric acid . H2SO4 (aq) + SO3 (g) H2S2O7 (l) H2S2O7 (l) + H2O (l) 2H2SO4 (aq)