2. 1 Chapter 3 Oceans 3.1 Introducing oceans and seas 3.2 Composition of sea water 3.3 Extraction of common salt from sea water 3.4 Tests for sodium and chloride ions in common salt 3.5 Tests for the presence of water in a sample 3.6 Electrolysis of sea water and uses of products Key terms Check your progress Experiment 3.1 — Solution

3. 2 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

4. Ocean and Sea

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% 3.2COMPOSITION OF SEA WATER (besides water) 4.2 Composition of sea water

6. 5 3.3EXTRACTION OF COMMON SALT FROM SEA WATER Common salt (sodium chloride) is the most abundant resource in sea water. 3.3 Extraction of common salt from sea water

7. 6 Common salt is the most important natural flavouring. Common salt is an important, useful substance at home and in industry.

8. 7 Chlorine bleach is one of the important industrial products obtained from common salt.

9. 8 EVAPORATION OF SEA WATER Evaporation salt 3.3 Extraction of common salt from sea water

10. 9 (a) Direct heating (b) Heating with a steam-bath heat sea water evaporating basin sea water evaporating basin steam water 3.3 Extraction of common salt from sea water wire gauze tripod

11. 10 PURE TO OBTAIN PURE SODIUM CHLORIDE 1. Filtration 2. Crystallization + Pure sodium chloride 3.3 Extraction of common salt from sea water

12. 11 glass rod sea water folded filter paper residue filter funnel filtrate stand 3.3 Extraction of common salt from sea water Filtration Firstly, any insoluble substances such as sand should be removed from sea water by filtration.

13. 12 3.3 Extraction of common salt from sea water Filtration of sea water ( represented by a mixture of copper(II) sulphate solution).

14. 13 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 saturated 2. Solution becomes saturated 3. Place a small crystal into the solution as ‘seed’ 3. Place a small crystal into the solution as ‘seed’ 4. Solid crystals slowly grow in size 4. Solid crystals slowly grow in size 3.3 Extraction of common salt from sea water

15. 14 ISOLATION OF PURE WATER FROM SEA WATER 4.3 Extraction of common salt from sea water Distillation involves boiling of a solution followed by condensation of the vapour formed. Distillation is used to separate a solvent with non-volatile solute. How do you separate a mixture of two liquids with different boiling points, like water and alcohol? Fractional distillation.

16. 15 Distillation using ‘Quickfit’ apparatus. STSE connections 3.2 heat thermometer pear-shaped flask anti-bumping granule solution Liebig condenser receiver adaptor test tube (as receiver) cold water in (from tap) water out (to sink) thermometer bulb distillate cold water Experiment 3.2

17. 16 Distillation of sea water 4.3 Extraction of common salt from sea water

18. 17 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

19. 18 TEST FOR SODIUM IONS (Flame Test) 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

20. 19 Flame tests of some metal chlorides. 4.4 Tests for sodium and chloride ions in common salt

21. 20 4.4 Tests for sodium and chloride ions in common salt Flame test is used to identify the metal part of a compound. potassium (lilac) sodium (brilliant golden yellow) calcium (brick red) copper (bluish green)

23. 22 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

24. 23 Test for the presence of chloride ions. 4.4 Tests for sodium and chloride ions in common salt

25. 24 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

26. 25 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.

27. 26 4.5 Tests for the presence of water in a sample Test for the presence of water by anhydrous copper(II) sulphate.

28. 27 Figure 4.19 Water turns blue cobalt chloride test paper pink. Blue cobalt chloride test paper test paper turns pink in the presence of water 4.5 Tests for the presence of water in a sample Water turns blue cobalt chloride test paper pink.

29. 28 Test for the presence of water by cobalt chloride test paper. 3.5 Tests for the presence of water in a sample

30. 29 Note that neither of the above tests shows that the sample under test is pure water. To prove it is pure water, we can carry out the boiling point test. If the liquid boils at 100°C (at 1 atmospheric pressure), it should be pure water.

31. 30 3.6ELECTROLYSIS OF SEA WATER AND USES OF PRODUCTS Decomposition by electricity electricity ELECTROLYSISELECTROLYSIS 3.6 Electrolysis of sea water and uses of products

32. 31 Fig.3.20 Electrolysis of sea water. Do you know? hydrogen gas graphite electrode (-) graphite electrode (+) chlorine gas sea water direction of electron flow

33. 32 Brine electrolysis margarine rocket fuel water sanitation bleach aluminium extraction soap hydrogenchlorinesodium hydroxide

34. 33 Brine electrolysis Other uses: make ammonia and fertilizers, make hydrochloric acid, etc. Other uses: make plastics (e.g. PVC), solvents, pesticides, etc. Other uses: paper industry, treatment of acidic / heavy metal effluents from factories. Fig.3.21 Some uses of products from the electrolysis of brine. hydrogenchlorine sodium hydroxide

35. 34 Sea water Uses: making margarine rocket fuel hydrochloric acid Uses: water treatment bleach plastic Uses: soap aluminium extraction paper making electrolysis Hydrogen ChlorineSodium hydroxide

36. 35 Sea water WATER Sodium chlorideOthers Dry cobalt chloride test paper / _______________ Pure water _____ sodium chloride Impure sodium chloride 68% 32% tested with distillation __________ anhydrous copper(II) sulphate ____________ evaporation 1.filtration 2.crystallization Pure Salts

37. 36 _____ sodium chloride Pure _______ ion Brilliant _____________ flame White precipitate tested with acidified ______________ consists of flame test Sodium Chloride golden yellow silver nitrate

38. 37 ENDEND Chapter 4 Oceans