Presentation on theme: "1 Huge Forces Cause Faults. 2 3 Fossil Zoom 4 Displacement A good way to compare the reactivity of metallic elements is by performing displacement reactions."— Presentation transcript:
4 Displacement A good way to compare the reactivity of metallic elements is by performing displacement reactions. A displacement reaction is one in which a more reactive element ‘takes the place of’ (displaces) a less reactive element. When zinc is added to aqueous copper sulfate solution, the zinc displaces the copper from the sulfate solution to form zinc sulfate and copper. This happens because zinc is more reactive than copper. Zinc (s) + copper sulfate (aq) zinc sulfate (aq) + copper (s) Zn (s) + CuSO 4(aq) ZnSO 4(aq) + Cu (s)
5 Displacing Copper Which elements in the reactivity series could displace copper from a solution of copper sulfate? How could you find out?
6 Lime Limestone consists mainly of the compound calcium carbonate. When limestone is heated to high enough temperatures (around 1500°C) it breaks up, it undergoes thermal decomposition. Industrially this happens in a lime kiln. Lime kilns produce vast quantities of calcium oxide, calcium oxide is known as lime or quicklime. Calcium carbonate calcium oxide + carbon dioxide CaCO 3(s) CaO (s) + CO 2(g) The word equation for this reaction is: The chemical equation for this reaction is:
7 Lime Kiln - Carbon Dioxide One of the products of the thermal decomposition of limestone in the lime kiln is carbon dioxide. Carbon dioxide is a greenhouse gas. The thermal decomposition of limestone in a lime kiln therefore increases the amount of this greenhouse gas in the atmosphere. What effects do greenhouse gases have on the Earth’s atmosphere? How do greenhouse gases alter the Earth’s climate? Task: In the region of five billion tonnes of limestone are produced annually across the globe. If 10% of this were thermally decomposed in a lime kiln how much carbon dioxide would be added to the Earth’s atmosphere by this process?
8 Chlorofluorocarbons Chlorofluorocarbons (also known as CFCs) are the notorious haloalkanes which are linked with ozone depletion. Examples are trichlorofluoromethane and dichlorodifluoromethane. CCl 3 FTrichlorofluoromethane CCl 2 F 2 Dichlorodifluoromethane
10 CFCs Properties Do you know any of the general properties of chlorofluorocarbons? They are very unreactive (chemically inert if you wish) - this is why they were previously very popular with scientists. The are non-flammable and non-toxic - so they were considered safe for people to use. They do not cause corrosion - so they could be used near to machinery. They are insoluble in water. They have low boiling points - so they vaporise easily.
11 CFCs Uses Do you know any of the uses of chlorofluorocarbons? Refrigerants - as CFCs have low boiling points, they were used in fridges and air-conditioning systems. Solvents - for example to clean electrical circuitry, as CFCs vaporise easily. Propellants - to force the contents out of aerosols. A major use has been in aerosol inhalers for drugs to treat asthma. Blowing agents - for example in the manufacture of polystyrene. The desire to stop using CFCs by scientists meant that safer alternatives had to be found.