How does chemistry help feed a growing population, and at what cost?
Fertilisers: the essential elements nitrogen, phosphorus and potassium, the Haber process for ammonia, the Ostwald process for nitric acid, nitrogen fixation, and environmental problems such as eutrophication.
An SQA National 5 Chemistry answer on fertilisers, covering the essential elements nitrogen, phosphorus and potassium, the Haber process for making ammonia, the Ostwald process for nitric acid, nitrogen fixation, and the environmental problem of eutrophication.
Reviewed by: AI editorial process; not yet individually human-reviewed
Have a quick question? Jump to the Q&A page
Jump to a section
What this key area is asking
The SQA wants you to know the essential elements that fertilisers supply, describe the Haber process for ammonia and the Ostwald process for nitric acid, explain nitrogen fixation, and discuss environmental problems such as eutrophication. It is a strongly applied key area connecting chemistry to feeding the world.
The essential elements
Nitrogen fixation
The Haber process
The Ostwald process
Environmental problems
Worked example: tracing the nitrogen
Examples in context
Industrial nitrogen fixation through the Haber process is one of the most important chemical achievements in history, because it allowed the mass production of fertilisers that feed a large part of the world's population. Before it, farmers relied on natural sources of nitrogen such as manure and clover, which fixes nitrogen through bacteria in its roots. The flip side is eutrophication, which is why farmers are now careful about how much fertiliser they apply and when, to keep it out of waterways.
Try this
Q1. Name the three essential elements supplied by NPK fertilisers. [1 mark]
- Cue. Nitrogen, phosphorus and potassium.
Q2. Name the raw materials combined in the Haber process. [1 mark]
- Cue. Nitrogen (from air) and hydrogen (from natural gas).
Q3. Explain why a fertiliser must be soluble. [1 mark]
- Cue. So the plant can take it up through its roots, which absorb dissolved nutrients.
Exam-style practice questions
Practice questions written in the style of SQA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
SQA N5 2019 style3 marksName the three essential elements that fertilisers provide, name the industrial process used to make ammonia, and name the two raw materials it combines.Show worked answer →
Markers reward the three elements, the named process, and the two raw materials.
The three essential elements provided by fertilisers are nitrogen, phosphorus and potassium, often written as NPK.
The industrial process used to make ammonia is the Haber process.
The Haber process combines nitrogen and hydrogen. The nitrogen is obtained from the air and the hydrogen is usually obtained from natural gas. They are reacted together under high pressure and a moderate temperature with an iron catalyst.
SQA N5 2021 style3 marksFertilisers help crops grow, but their overuse can damage rivers and lochs. Explain how fertiliser run-off leads to eutrophication, and state why nitrogen compounds are needed in the first place.Show worked answer →
A 3 mark answer needs the run-off and algae idea, the oxygen depletion, and the reason nitrogen is needed.
When excess fertiliser washes off fields into rivers and lochs, the extra nitrogen and phosphorus make algae grow very quickly, forming an algal bloom that covers the water surface.
When the algae die, microorganisms break them down and use up the dissolved oxygen in the water. With the oxygen gone, fish and other aquatic life suffocate and die. This sequence is called eutrophication.
Nitrogen compounds are needed because plants require nitrogen to make proteins for growth, and growing crops remove nitrogen from the soil, which the fertiliser replaces.
Related dot points
- Metals: properties and uses, the reactivity series, reactions with oxygen, water and acids, displacement reactions, and oxidation and reduction with ion-electron equations.
An SQA National 5 Chemistry answer on metals, covering their properties and uses, the reactivity series, reactions with oxygen, water and dilute acids, displacement reactions, and oxidation and reduction with ion-electron equations.
- Plastics: synthetic materials made by addition polymerisation, monomers and polymers, the repeating unit, uses of common plastics, and the problems of disposal.
An SQA National 5 Chemistry answer on plastics, covering synthetic materials, addition polymerisation, monomers and polymers, the repeating unit, the uses of common plastics, and the problems of plastic disposal.
- Nuclear chemistry: alpha, beta and gamma radiation and their properties, radioactive decay as a random process, half-life and half-life calculations, and the uses and dangers of radiation.
An SQA National 5 Chemistry answer on nuclear chemistry, covering alpha, beta and gamma radiation and their penetrating power, radioactive decay as a random process, half-life and half-life calculations, and the uses and dangers of nuclear radiation.
- Chemical analysis: general practical techniques, gas tests and flame tests, paper chromatography, and the use of analysis to monitor the environment.
An SQA National 5 Chemistry answer on chemical analysis, covering general practical techniques, the standard gas tests for hydrogen, oxygen and carbon dioxide, flame tests for metal ions, paper chromatography, and the use of analysis to monitor the environment.
- Overview of Area 3 Chemistry in Society: how metals, electrochemical cells, metal extraction, plastics, fertilisers, nuclear chemistry and chemical analysis connect.
An SQA National 5 Chemistry overview of Area 3 Chemistry in Society, linking metals and redox, electrochemical cells, metal extraction, plastics, fertilisers, nuclear chemistry and chemical analysis into the applied chemistry of materials, industry and analysis.
Sources & how we know this
- SQA National 5 Chemistry Course Specification — SQA (2019)