2Useful Air What is air? Manufacture of ammonia ContentsUseful AirWhat is air?Manufacture of ammoniaManufacture of fertilizerFertilizers and the environmentSummary activities
3Around 78% of the air is nitrogen. About 21% is oxygen. What is air made of?Around 78% of the air is nitrogen.About 21% is oxygen.The remaining 1% is mostly argon (0.93%), with carbon dioxide (0.04%) and varying amounts of water vapour.
5Separating gasesHere are the boiling points of the three main gases in air:nitrogen: –196ºCoxygen: –183ºCargon: –186ºCWhen air is distilled:Which gas will boil first?Which gas will there be most of?Which gas will there be least of?nitrogennitrogenargon
6Useful Air What is air? Manufacture of ammonia ContentsUseful AirWhat is air?Manufacture of ammoniaManufacture of fertilizerFertilizers and the environmentSummary activities
7Nitrogen and ammoniaNitrogen is a very unreactive gas which tends to react slowly if at all.Changing the element nitrogen into compounds that plants can absorb involves reacting the nitrogen with hydrogen to form ammonia.nitrogen hydrogen ammoniaN H 2NH3
8The Haber process (1)Can you suggest ways of speeding up the reaction of nitrogen with hydrogen?Use a catalystUse a high temperatureCompress the gasesThe actual conditions used are:An iron catalystA temperature of 450oCA pressure of 200 atmospheres
9nitrogen + hydrogen ammonia The Haber process (2)Even under these conditions only part of the nitrogen and hydrogen react to form ammonia.If the temperature is raised too high the ammonia increasingly decomposes back into the reactants. The reaction is said to be reversible.nitrogen + hydrogen ammoniaGetting the best rate of conversion into ammonia involves a very careful choice of reaction conditions.
10The Haber processThe Haber process gives a mixture of reactants and products.Here are the boiling points of the substances involved.Which one most easily turns into a liquid?nitrogenhydrogenammoniaHow might ammonia be separated from unreacted nitrogen & hydrogen?°C
11The Haber processUse this animation if you wish to show the process step by step.
12The Haber processUse this animation if you wish to show the process as a whole
14Useful Air What is air? Manufacture of ammonia ContentsUseful AirWhat is air?Manufacture of ammoniaManufacture of fertilizerFertilizers and the environmentSummary activities
15Uses of ammoniaThe majority of ammonia is used for the manufacture of fertilizers, but there are other uses.
16Ammonia and fertilizers Ammonia is sometimes pumped directly into the soil as a fertiliser but because it is a gas much of it may escape.More usually some of the ammonia is reacted with oxygen to form nitric acidNH O2 HNO3 + H2OThis nitric acid is then reacted with more ammonia to give solid ammonium nitrateHNO NH3 NH4NO3
17Manufacture of ammonium nitrate Use this animation if you wish to show the process step by step.
18Manufacture of ammonium nitrate Use this animation if you wish to show the process step by step.
20Useful Air What is air? Manufacture of ammonia ContentsUseful AirWhat is air?Manufacture of ammoniaManufacture of fertilizerFertilizers and the environmentSummary activities
21Ammonia and fertilizer What are the advantages and disadvantages of different types of fertilizer?
22The effects of fertilizer In a group of 3 or 4 write the words ‘The effects of fertilizer’ in the middle of a piece of A3 paper.Around the outside write down all of the effects – good and bad - that fertilizers can have on the environment.
23Advantages of fertilizers They have madenaturallyinfertile soilssuitable foragriculture. Thishas beensignificant inpoorer parts ofthe world.They eliminate the need to allow fields to lie fallow and for crop rotation. Thisenhances theproductivity of the land.They increase the yield of the cropsproduced.This has allowed more land to be set aside for nature conservation and recreation.
24Disadvantages of fertilizers Fertilizers applied to farm landToo much used, at the wrong time of year, during wet weather,ifexcessWashed intorivers and lakescausesContaminatesundergrounddrinking watersuppliescausesExcessive growth of aquatic plants.The bacteria which live on dead plants thrive and use up the oxygen in the water. The lack of oxygen causes death of fish. This is called eutrophication.Harm to infants - called‘blue baby’ syndrome
25GrowmoreGrowmore is an NPK fertiliser (7-7-7) containing about 7% nitrogen, 7% phosphorous and 7% potassium.
26NPK fertilizersNitrogen (N) - needed for proteins in leaves and stalks.Phosphorous (P) - speeds up growth of roots and helps fruit to ripen.Potassium (K) - speeds up seed growth and improves resistance to disease.
27A problem for Farmer Giles Farmer Giles has been accused of raising nitrate levels in local water by using too much fertilizer.Here are some suggestions from other locals.Are they good or bad?Split the fertilizer over 3 applications instead of just one.Use a more soluble fertilizer so that it gets into the plants more easily.Check the weather forecast and avoid applying fertilizer before rain is due.Grow a quick crop of legumes instead of using a nitrogen-containing fertilizer.Use fertilizer with larger particle size.
28AnswersThree applications instead of just one – good Plants get time to take in each application.More soluble fertilizer – badIt will dissolve in rain and wash into local drains.3. Avoid applying it before rain is due – goodThis means it won’t dissolve in the rain and wash into drains.4. Grow a quick crop of legumes – goodBut depends on timings of crops, etc.5. Use fertilizer with larger particle size – goodUsing the same amount of fertilizer with larger particles is likely to lead to a slower dissolving into the ground, giving plants more time to absorb it.
29Useful Air What is air? Manufacture of ammonia ContentsUseful AirWhat is air?Manufacture of ammoniaManufacture of fertilizerFertilizers and the environmentSummary activities
30Glossaryair – A mixture of gases containing mainly nitrogen and oxygen, but with small amounts of other gases.ammonia – A gas used in the manufacture of fertilizer and nitric acid.catalyst – A substance that changes the rate of a reaction without being used up.eutrophication – Excess plant growth in water leading to reduced oxygen levels, caused by increased nutrient levels.fertilizer – A substance added to soil to increase its productivity.Haber process – The industrial process used to manufacture ammonia from nitrogen and hydrogen.NPK – A type of fertilizer containing nitrogen, phosphorous and potassium.