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2. The units in this module are: Click on the links to take to the topic you wish to revise. C4a – Acids and bases C4b – Reacting masses C4c – Fertilisers and crop yield C4d – Making ammonia C4e – Detergents C4f – Batch or continuous C4g – Nanochemistry C4h – How pure is our water Next page

3. Properties of acids and bases Neutralisation Naming salts Reactions of acids Main menu Next page

4. Properties of Acids and Bases Main menu Back to C4a less than 7 H + ions Acids are substances that have a pH of less than 7. They contain H + ions. opposite greater than 7 Bases are the chemical opposite of acids. They have a pH greater than 7. They are usually oxides or hydroxides. alkalisOH - ions The bases that are soluble are called alkalis. These contain OH - ions. pH universal indicator To determine the pH of a solution you add a few drops of universal indicator. Next page

5. Neutralisation Main menu Back to C4a opposite cancel Because acids and bases are chemically opposite, if they are added in the right amounts they will cancel each other out. neutralisation This is called neutralisation. Acid + Base  Salt + Water For example Hydrochloric acid + Potassium hydroxide  Potassium chloride + Water HCl + KOH  KCl + H 2 O HCl + KOH  KCl + H 2 O In summary, H + + OH -  H 2 O H + + OH -  H 2 O (acid) (alkali) (water) (acid) (alkali) (water) Next page

6. Naming Salts Main menu Back to C4a salt The salt that is formed during a neutralisation reaction depends on the chemicals we use. Hydrochloricchloride Hydrochloric acid makes a chloride salt Sulphuricsulphate Sulphuric makes a sulphate salt Nitricnitrate Nitric acid makes a nitrate salt The rest of the name comes from the metal compound is reacting with acid sodium hydroxide + nitric acid  sodium nitrate + water Next page

7. Reactions of Acids Main menu Back to C4a Acids react with lots of different chemicals. General equations show how they react Metal + Acid  Salt + Hydrogen Metal oxide + Acid  Salt + Water Metal hydroxide + Acid  Salt + Water Metal carbonate + Acid  Salt + Carbon dioxide + Water Next page

8. Click here to take you to a quiz on “Properties of acids and bases” Main menu Next page

9. Relative atomic mass Relative formula mass Reacting masses % yield Main menu Next page

10. Main menu Back to C4b Relative Atomic Mass small compared Atoms are too small to obtain their actual mass. A more useful mass is the mass of the atom compared to carbon. Each element on the periodic table has two numbers. top number The top number is the relative atomic mass Next page

11. Main menu Back to C4b Relative Formula Mass compound The relative formula mass is the mass of a compound. We work it out like this: H1x 2= 2 S32x 1= 32 O16x 4= 64 = 98 Write the symbols Identify relative atomic mass Multiply by number of atoms Add them all up Next page

12. Main menu Back to C4b Reacting Masses how much used upproduced Sometimes we need to be able to work out how much of a substance is used up or produced. e.g.: How much calcium oxide is produced from 50kg calcium carbonate Step 1 : write the equation CaCO 3  CaO + CO 2 Step 2 : fill in the information that we know CaCO 3  CaO + CO 2 50 kg  ? Step 3 : add relative formula masses CaCO 3  CaO + CO 2 50 kg  ? 100 56 Step 4 : work out the ratio CaCO 3  CaO + CO 2 50 kg  ? 100 56 divide by 2 Answer = 28kg of calcium oxide Next page

13. Main menu Back to C4b % Yield Yield Yield describes how much of a product has been made. predicted yield We can work out a predicted yield by using reacting masses. actual yield If we collect and weigh the product, we have the actual yield. lost% yield Some product is usually lost so we can work out a % yield. The higher this is the better. % yield = (actual yield / predicted yield) x 100 E.g. Sodium is reacted with chlorine. 23.4g of sodium chloride is made. It was expected to form 29.5g. % yield = 23.4 x 100 = 80% 29.5 Next page

14. Main menu Click here to take you to a quiz on “Reacting masses” Next page

15. What are fertilisers? Problems with fertilisers Making a fertiliser Percentage mass Main menu Next page

16. Main menu Back to C4c What are fertilisers? essential elements fastercrop yield. Fertilisers are chemicals that provide essential elements for plant growth. They make crops grow faster and increase crop yield. The three main essential elements are: N, nitrogen P, phosphorus K, potassium soluble absorbed It is important that fertilisers are soluble in water so they can be absorbed by the plant. ammonium sulphate, (NH 4 ) 2 SO 4 ammonium nitrate, NH 4 NO 3 Examples of fertilisers are ammonium sulphate, (NH 4 ) 2 SO 4 and ammonium nitrate, NH 4 NO 3 Next page

17. Main menu Back to C4c Problems with Fertilisers Overuse eutrophication Overuse of fertilisers can cause problems such as eutrophication. lakes/rivers algae Fertilisers used by farmers may be washed into lakes/rivers. This can increase the growth of algae on the top. algal bloomsunlight die The algal bloom stops sunlight getting to the plants, causing them to die. increase oxygen The number of aerobic bacteria increase and they use up the oxygen which means there is none for fish and other aquatic animals. Next page

18. Main menu Back to C4c Making a Fertiliser neutralising Fertilisers can be made by neutralising an acid with an alkali. alkali 1. Measure out the alkali neutral 2. Add acid until it is neutral (pH 7) Evaporate 3. Evaporate the solution slowly until crystals form on the end of a glass rod placed in solution Filter 4. Filter crystals from the solution 5. Remove the crystals, wash them and leave them to dry Next page

19. Main menu Back to C4c Percentage Mass percentage mass We can calculate the percentage mass of an element in a compound using % mass = mass of element x 100 relative formula mass Example What is the % mass of nitrogen in ammonium nitrate, NH 4 NO 3, fertiliser? Calculate the relative formula mass = 80 35% % mass = N x 2 x 100 = 28 x 100 = 35% NH 4 NO 3 80 Next page

20. Click here to take you to a quiz on “Fertilisers and crop yield” Main menu Next page

21. Uses of ammonia The Haber process Conditions for the Haber process Factors affecting cost Main menu Next page

22. Back to C4d Main menu Uses of Ammonia hydrogennitrogen Ammonia is a gas made from hydrogen and nitrogen The reaction is N 2 + 3 H 2 2 NH 3 reversible The means it is a reversible reaction. cleaning fluids, hair dyes, nitric acid and fertilisers Ammonia has many uses including cleaning fluids, hair dyes, nitric acid and fertilisers Next page

23. Main menu Back to C4d The Haber Process hydrogennitrogen Ammonia is a gas made from hydrogen and nitrogen mixed ammonia The nitrogen and hydrogen is mixed together to form ammonia gas. liquid condensed We need the ammonia to be a liquid so it is condensed. recycled Not all of the raw materials have been converted to ammonia. The unreacted gases are recycled. Next page

24. Main menu Back to C4d Conditions for the Haber Process yield So that we get the best yield of ammonia, certain conditions must be used. low temperature 450C Ideally a low temperature would give the best yield but the reaction would be slow so we compromise and use 450C high pressure 200 atmospheres A high pressure would give the best yield but the equipment is very expensive so we use 200 atmospheres. iron catalyst We also use an iron catalyst to make the reaction faster Next page

25. Main menu Back to C4d Factors Affecting Cost cost best yieldlowest cost Industry is concerned with cost. We need to use conditions that allow the best yield of product at the lowest cost. rate of reaction The rate of reaction needs to be high to produce a good daily yield and the percentage yield must be high. Other costs include: Labour costs Labour costs (wages) Cost of reactants Cost of reactants (starting materials) Cost of equipment Cost of equipment (machines) Next page

26. Main menu Click here to take you to a quiz on “Making ammonia” Next page

27. What’s in washing products How do detergents work? Dry cleaning Main menu Next page

28. Main menu Back to C4e What’s in Washing Products Washing products are a mixture of lots of different chemicals. Washing Powder Washing up liquids Detergent This is what does the cleaningDetergent Bleach To remove coloured stainsWater To dissolve and dilute the detergent Water softener To soften hard water Water softener To soften hard water Optical brightener To make whites appear whiter Rinse agent To help water drain off so it dries quickly Enzymes To break up food and protein stains Colour & fragrance To make it more attractive to buy Next page

29. Main menu Back to C4e How Detergents Work hydrophilic Detergent molecules have two parts. The negatively charged ‘head’ is attracted to water so it is hydrophilic. hydrophobic The tail is not charged and is not attracted to water so it is hydrophobic. hydrophobicrepelled oil droplet The hydrophobic end of the detergent molecule is repelled by the water causing it to stick to the oil droplet. lifted As more detergent molecules are absorbed into the oil droplet, the oil is lifted washed away When the oil droplet is totally surrounded it can be washed away leaving the object clean Next page

30. Main menu Back to C4e Dry Cleaning insoluble Some stains are insoluble in water and so normal cleaning can not be used. Dry cleaning Dry cleaning is used instead. The clothes are still washed in a liquid but it is not water. solvents Different solvents dissolve different stains. intermolecular broken Stains will be cleaned if the intermolecular forces in the stain are able to be broken. Next page

31. Main menu Click here to take you to a quiz on “Detergents” Next page

32. Batch processes Continuous processes Making medicines Developing medicines Main menu Next page

33. Main menu Back to C4f Batch Processes In this the reactants are put in a reaction vessel. The reaction happens and the product is removed. Medicinespharmaceutical Medicines and pharmaceutical drugs are often made in batches Batch processes: Make a product on demand Make a product on a small scale Can make a variety of products Are labour intensive because the reactor needs to be filled, emptied and cleaned Usually requires specialists to make the products Next page

34. Main menu Back to C4f Continuous Processes reactants product In this the reactants are continually being fed into a large reactor and the product is continually being produced and collected at the same time (like a conveyor belt) Continuous processes: Operate all the time Make a product on a large scale Are dedicated to making just one product Can run automatically so low labour costs Next page

35. Main menu Back to C4f Making Medicines synthetic extracted Materials used to make medicines can be synthetic or they can be extracted from natural sources like plants. To extract a small amount of material -crushed -the plant is crushed using a pestle and mortar -solventdissolve -a solvent is added to dissolve the material -chromatography -the solution is put onto chromatography paper and separate allowed to separate Next page

36. Developing Medicines Main menu Back to C4f 10 to 15 years It takes a long time – 10 to 15 years – from discovering a material to being able to use it on a patient. The stages are: ResearchCostly because highly qualified staff are needed as decisions need to be made DevelopmentImportant to increase the effectiveness of the drug TestedTo check it works as intended and safely. Tested first on animals and then humans Legal requirements Medicines are costly because the raw materials may be rare or require complex methods to extract them Next page

37. Main menu Click here to take you to a quiz on “Batch and continuous” Next page

38. Allotropes Diamond Graphite Fullerenes Nanotubes Uses of nanochemistry Main menu Next page

39. Main menu Back to C4gAllotropes different forms Allotropes are different forms of the same element where the atoms are arranged differently. carbon Diamond, graphite, fullerenes and nanotubes are all allotropes of carbon. Next page

40. Main menu Back to C4gDiamond rigid Diamond has a rigid structure does not conduct free It does not conduct electricity because it doesn’t have any free electrons. insoluble It is insoluble in water. transparentlustrous It is used in jewellery because it is transparent and lustrous. high melting point strong Has a very high melting point because of the strong covalent bonds Next page

41. Main menu Back to C4gGraphite layered Graphite has a layered structure insoluble It is insoluble in water black It is black which is why it is used in pencils conducts electricity free It conducts electricity because it has free electrons between two layers high melting point strong It has a high melting point because of the strong covalent bonds slide weak intermolecular forces The layers can slide over each other because of weak intermolecular forces between the layers Next page

42. Main menu Back to C4gFullerenes 60 carbon sphere These are an allotrope that consists of 60 carbon atoms arranged in a sphere. They are sometimes called “Bucky balls”. black solid It is a black solid red solution petrol It makes a red solution when it is dissolved in petrol. Next page

43. Main menu Back to C4gNanotubes joining fullerenes hexagons Nanotubes were made by joining fullerenes together. They are hexagons curled into a tube. conduct electricity strong They conduct electricity and are very strong. tennis rackets semiconductors catalysts They are used to reinforce graphite tennis rackets, make semiconductors in modern computers and to develop new, more efficient catalysts Next page

44. Main menu Back to C4g Uses of Nanochemistry small scale Nanochemistry involves materials on a very small scale. Scientists are interested in buckminster fullerenes and nanotubes cageinside This is because they can be used to cage other molecules inside them. drugs They will be useful for drugs. For example a major new HIV treatment uses “Bucky balls” to deliver a material which disrupts the way the virus works. Next page

45. Main menu Click here to take you to a quiz on “Nanochemistry” Next page

46. Sources of water Water treatment What’s in your water? Identifying dissolved ions Main menu Next page

47. Main menu Back to C4h Sources of Water water There are lots of places we can obtain water, but the four main sources are: rivers, lakes, reservoirs, aquifers(wells) drinkingwashing Water is important for drinking, washing and other jobs in the home. coolingsolvent It is also important in industry for cooling, as a solvent or as a raw material. granted We take clean water for granted but many parts of the developing world still do not have clean water. Next page

48. Main menu Back to C4h Water Treatment purifysafe Water has to be treated to purify it and make sure it is safe to drink before it reaches the home. insoluble particles, pollution, microorganisms, dissolved salts and minerals Untreated water can contain insoluble particles, pollution, microorganisms, dissolved salts and minerals. sedimentationfiltration chlorination A typical treatment involves sedimentation, filtration and then chlorination. Next page

49. Main menu Back to C4h What’s in your Water? pollutants Even after it has been purified there can still be pollutants in the water as they are harder to remove. They include: -nitrates -nitrates from fertilisers -lead compounds -lead compounds from old pipes in the plumbing -pesticides -pesticides from spraying crops Next page

50. Main menu Back to C4h Identifying Dissolved Ions dissolved ions precipitation The dissolved ions of some salt in water are easy to recognise as they undergo precipitation reactions. Sulphatesbarium chloride white Sulphates can be detected using barium chloride solution – a white precipitate forms Silver nitrate Silver nitrate can be used to identify halide ions (group 7) With silver nitrate: -chlorideswhite -chlorides form a white precipitate -bromidescream -bromides form a cream precipitate -iodidesyellow -iodides form a yellow precipitate Next page

51. Main menu Click here to take you to a quiz on “How pure is our water” Next page