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Debate : fertiliser use

Divide the class into two groups to debate the following topic:

Increasing the use of artificial fertilisers is the best solution to meet the growing food needs of the world's human population.

One group should take the position of agreeing with the statement, and the other should disagree . In your groups, discuss reasons why you have the opinion that you do, and record some notes of your discussion. Your teacher will then explain to you how to proceed with the debate.

The following presentation shows other ways to represent the nitrogen cycle.

Summary

  • Nitrogen is essential for life on earth, since it forms part of amino acids , proteins and nucleic acids .
  • The atmosphere is composed mostly of nitrogen gas, but the gas is inert , meaning that it is not available to living organisms in its gaseous form.
  • The nitrogen cycle describes how nitrogen and nitrogen-containing compounds are changed into different forms in nature.
  • The nitrogen cycle consists of three major processes: nitrogen fixation , nitrification and denitrification .
  • Nitrogen fixation is the conversion of atmospheric nitrogen into compounds such as ammonia that are more easily used.
  • Nitrogen can be fixed biologically through the actions of bacteria , industrially through the Haber-Bosch process or by lightning .
  • Nitrification converts ammonia into nitrites and nitrates , which can be easily assimilated by plants.
  • Denitrification converts nitrites and nitrates back into gaseous nitrogen to complete the nitrogen cycle.
  • Humans have had a number of impacts on the nitrogen cycle. The production of artificial fertilisers for example, means that there is a greater chance of runoff into water systems. In some cases, eutrophication may occur.
  • Eutrophication is the contamination of a water system with excess nurtrients, which stimulates excessive algae growth at the expense of other parts of the ecosystem. This occurs as eutrophication reduces oxygen levels in the water.
  • Many nitrogen gases such as NO, N 2 O and NO 2 are released by agricultural soils and artificial fertilisers. These gases may combine with water vapour in the atmosphere and result in acid rain . Some of these gases are also greenhouse gases and may contribute towards global warming .
  • A number of industrial processes are used to produce articifical fertilisers .
  • The Haber-Bosch process converts atmsopheric nitrogen into ammonia .
  • The Ostwald process reacts ammonia with oxygen to produce nitric acid , which is used in the preparation of fertilisers and explosives.
  • If ammonia and nitric acid react, the product is ammonium nitrate , which is used as a fertiliser and as an explosive.

Summary exercise

  1. Look at the diagram and the descriptions of the nitrogen cycle earlier in the chapter:
    1. Would you describe the changes that take place in the nitrogen cycle as chemical or physical changes? Explain your answer.
    2. Are the changes that take place in the water cycle physical or chemical changes? Explain your answer.
  2. Explain what is meant by each of the following terms:
    1. nitrogen fixing
    2. fertiliser
    3. eutrophication
  3. Explain why the fixing of atmospheric nitrogen is so important for the survival of life on earth.
  4. Refer to the diagram below and then answer the questions that follow:
    1. Explain the role of decomposers in the nitrogen cycle.
    2. If the process taking place at (3) is nitrification , then label the processes at (1) and (5).
    3. Identify the nitrogen products at (2) and (4).
    4. On the diagram, indicate the type of bacteria that are involved in each stage of the nitrogen cycle.
    5. In industry, what process is used to produce the compound at 2?
    6. Does the diagram above show a 'cycle'? Explain your answer.
  5. NO and NO 2 are both nitrogen compounds:
    1. Explain how each of these compounds is formed?
    2. What effect does each of these compounds have in the environment?
  6. There are a number of arguments both 'for' and 'against' the use of artificial fertilisers. Draw a table to summarise the advantages and disadvantages of their use.

Questions & Answers

I'm interested in biological psychology and cognitive psychology
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Communication is effective because it allows individuals to share ideas, thoughts, and information with others.
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Every time someone flushes a toilet in the apartment building, the person begins to jumb back automatically after hearing the flush, before the water temperature changes. Identify the types of learning, if it is classical conditioning identify the NS, UCS, CS and CR. If it is operant conditioning, identify the type of consequence positive reinforcement, negative reinforcement or punishment
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Source:  OpenStax, Siyavula textbooks: grade 10 physical science. OpenStax CNX. Aug 29, 2011 Download for free at http://cnx.org/content/col11245/1.3
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