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1 Chapter 4Oceans 4.1Introducing oceans and seas 4.2Composition of sea water 4.3Extraction of common salt from sea water 4.4Tests for sodium and chloride.

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Presentation on theme: "1 Chapter 4Oceans 4.1Introducing oceans and seas 4.2Composition of sea water 4.3Extraction of common salt from sea water 4.4Tests for sodium and chloride."— Presentation transcript:

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2 1 Chapter 4Oceans 4.1Introducing oceans and seas 4.2Composition of sea water 4.3Extraction of common salt from sea water 4.4Tests for sodium and chloride ions in common salt 4.5Tests for the presence of water in a sample 4.6Electrolysis of sea water and uses of products Summary Concept map Chapter 4Oceans

3 2 4.1INTRODUCING OCEANS AND SEAS Large area of salty water OCEANSOCEANS SEASSEAS Enclosing its continents and islands Enclosing its continents and islands Covers the Earth’s surface 4.1 Introducing oceans and seas

4 3 Figure 4.1 The Earth is the ‘water planet’ in our solar system. 70% of it is covered by water and 97% of this water occurs in oceans and seas! 70% of it is covered by water and 97% of this water occurs in oceans and seas! 4.1 Introducing oceans and seas

5 4 Figure 4.2 The salt composition by weight of a typical sea water sample. ______________ common salt (sodium chloride) 68% magnesium chloride 14.6% sodium sulphate 11.4% calcium chloride 3.1% other salts 2.9% 4.2COMPOSITION OF SEA WATER 4.2 Composition of sea water

6 5 4.3EXTRACTION OF COMMON SALT FROM SEA WATER Common salt (sodium chloride) is the most abundant resource in sea water. 4.3 Extraction of common salt from sea water

7 6 Figure 4.3 Common salt is the most important natural flavouring. 4.3 Extraction of common salt from sea water

8 7 Figure 4.4 Many useful chemicals can be obtained from common salt in chlor-alkali industry. 4.3 Extraction of common salt from sea water

9 8 EVAPORATION OF SEA WATER Figure 4.5 Common salt can be obtained from sea water by evaporation. Evaporation salt 4.3 Extraction of common salt from sea water

10 9 Figure 4.6 Getting common salt from sea water in the laboratory. (a) Direct heating (b) Heating with a steam-bath heat sea water evaporating basin sea water evaporating basin steam water 4.3 Extraction of common salt from sea water wire gauze tripod

11 10 TO OBTAIN PURE SODIUM CHLORIDE 1. Filtration 2. Crystallization + Pure sodium chloride 4.3 Extraction of common salt from sea water

12 11 Filtration Firstly, any insoluble substances such as sand should be removed from sea water by filtration. 1.Pour sea water onto filter paper 2.Use a glass rod to guide the flow 3. Small particles pass through as filtrate 4.Larger insoluble particles are retained as residue 4.3 Extraction of common salt from sea water

13 12 Figure 4.7 A piece of filter paper is folded into a conical shape and placed in a funnel. filter paper fold one layerthree layers filter funnel 4.3 Extraction of common salt from sea water

14 13 glass rod sea water folded filter paper residue filter funnel filtrate stand Figure 4.8 Filtration of sea water. 4.3 Extraction of common salt from sea water

15 Extraction of common salt from sea water Filtration of sea water.

16 15 Crystallization After the removal of insoluble impurities, pure crystals of common salt can be separated out by crystallization. 1. Evaporate slowly at room temperature 1. Evaporate slowly at room temperature 2. Solution becomes more concentrated 2. Solution becomes more concentrated 3. Solution becomes saturated 3. Solution becomes saturated 4. Solid crystals slowly grow in size 4. Solid crystals slowly grow in size 4.3 Extraction of common salt from sea water

17 16 sea water more concentrated solution solution saturated with respect to sodium chloride sodium chloride crystals Water slowly evaporates at room temperature Figure 4.10 Crystallization from sea water by slow evaporation. 4.3 Extraction of common salt from sea water

18 17 ISOLATION OF PURE WATER FROM SEA WATER How How to obtain pure water water from sea water? By Distillation 4.3 Extraction of common salt from sea water

19 18 Distillation involves boiling of a solution followed by condensation of the vapour formed. 4.3 Extraction of common salt from sea water

20 19 Figure 4.11 Distillation of sea water using simple apparatus. 4.3 Extraction of common salt from sea water pure water (distillate) end of delivery tube should be above distillate receiver test tube delivery tube water (cooling agent) heat anti-bumping granule (to prevent ‘bumping’ of solution) sea water boiling tube clamp thermometer

21 20 Distillation of sea water (copper(II) sulphate solution) using simple apparatus. 4.3 Extraction of common salt from sea water

22 21 Figure 4.13 The desalting plant at Lok On Pai had been sold to a foreign country. To obtain fresh water from sea water on a large scale 4.3 Extraction of common salt from sea water

23 22 4.4TESTS FOR SODIUM AND CHLORIDE IONS IN COMMON SALT Identification CHEMICAL ANALYSIS Composition 4.4 Tests for sodium and chloride ions in common salt

24 23 TEST FOR SODIUM IONS 4.4 Tests for sodium and chloride ions in common salt Figure 4.15 Performing a flame test to identify metal ions in a sample. (b) non-luminous flame sample of the salt to be tested (c) flame colour due to metal ions (a) platinum wire concentrated hydrochloric acid

25 Tests for sodium and chloride ions in common salt Figure 4.16 Flame colours of some metal ions. potassium (lilac) sodium (brilliant golden yellow) calcium (brick red) copper (bluish green)

26 Tests for sodium and chloride ions in common salt Sodium compounds give a brilliant golden yellow flame in the flame test. Calcium compounds give a brick red colour.

27 26 TEST FOR CHLORIDE IONS Figure 4.17 Silver nitrate test for the presence of chloride ions. 4.4 Tests for sodium and chloride ions in common salt white precipitate of silver chloride sea water add silver nitrate solution followed by excess dilute nitric acid

28 27 4.5TESTS FOR THE PRESENCE OF WATER IN A SAMPLE Anhydrous copper(II) sulphate powder Dry cobalt chloride test paper Waterpresent? 4.5 Tests for the presence of water in a sample

29 28 Figure 4.18 Water turns white anhydrous copper(II) sulphate blue. 4.5 Tests for the presence of water in a sample anhydrous copper(ll) sulphate watch glass water add a few drops of water Water turns white anhydrous copper(II) sulphate blue.

30 29 Figure 4.19 Water turns blue cobalt chloride test paper pink. in the presence of water Blue cobalt chloride test paper test paper turns pink 4.5 Tests for the presence of water in a sample Water turns blue cobalt chloride test paper pink.

31 30 4.6ELECTROLYSIS OF SEA WATER AND USES OF PRODUCTS Decomposition by electricity ELECTROLYSISELECTROLYSIS 4.6 Electrolysis of sea water and uses of products

32 31 For example chlorine sodium hydroxide sodium hydroxide hydrogen electrolysis 4.6 Electrolysis of sea water and uses of products Sea water

33 32 Figure 4.21 Membrane cells in ICI chlor-alkali plant in Malaysia. 4.6 Electrolysis of sea water and uses of products

34 33 Q4.1 In the chlor-alkali industry, brine, but not sea water, is electrolysed. Explain why. 4.6 Electrolysis of sea water and uses of products

35 34 A4.1 Both brine and sea water are a concentrated solution of sodium chloride. Brine is prepared by dissolving rock salt (sodium chloride) in water, so it does not contain other salts. Sea water is natural. Besides sodium chloride, it contains other dissolved salts as well. It is more suitable to electrolyse brine in chlor-alkali industry, since the concentration of sodium chloride can be increased to a high level as desired. 4.6 Electrolysis of sea water and uses of products

36 35 Hydrogen Chlorine Sodium hydroxide Brine electrolysis 4.6 Electrolysis of sea water and uses of products Figure 4.22 Some uses of products from the electrolysis of brine. ammonia (used to make fertilizers) MARGARINE food industry HCl hydrochloric acid rocket fuel HCl hydrochloric acid water treatment for sanitation plastic (e.g. PVC) solvents bleach chemicals (e.g. dyes & pesticides) treatment of acidic effluents from factories paper making aluminium extraction soap

37 36 Summary 1.Sea water contains about 3.5% by weight of dissolved substances. The main solute in sea water is common salt (sodium chloride). 2.Pure common salt can be extracted from sea water by filtration and crystallization. 3.Pure water can be isolated from sea water by distillation. Summary Composition of sea water Obtaining common salt and pure water from sea water

38 37 4.Distillation involves boiling of a solution followed by condensation of the vapour formed. 5.During distillation, the pure liquid that distils over is called the distillate; the solid left behind is called the residue. Summary

39 38 Test for sodium ions 6.Some metals can be identified by the flame test. Some characteristic flame colours are: Summary

40 39 7.To test for chloride ions in sea water, we add silver nitrate solution, acidified with excess dilute nitric acid, to a sample. A white silver chloride precipitate forms if chloride ions are present. Summary Test for chloride ions

41 40 8.Anhydrous copper(II) sulphate and dry cobalt chloride test paper can be used to detect the presence of water in a given sample. Test for water Summary

42 41 9.Electrolysis of brine produces useful chemicals: hydrogen, chlorine and sodium hydroxide. Refer to Figure to 4.22 for their uses. Summary Electrolysis of brine

43 42 Concept map Complete the following concept map. Uses:  food industry  hydrochloric acid  rocket fuel Uses:  water treatment  plastic  bleach Uses:  paper making  aluminium  soap Sea water electrolysis HydrogenChlorine Sodium hydroxide

44 43 WATER Cobalt chloride test paper / ____________ Pure water tested with Sodium chloride Others 68%32% Concept map Salts distillation anhydrous copper(II) sulphate

45 44 ______ sodium chloride Impure sodium chloride 1. filtration 2. crystallization ________ consists of _______ ion Brilliant ___________ flame White precipitate flame test tested with acidified ____________ Concept map evaporation Pure SodiumChloride silver nitrate golden yellow

46 45 ENDEND Chapter 4 Oceans


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