Nitrify ammonium into nitrate
Nitrifying microorganisms convert ammonium compounds into nitrate ions, making a form of nitrogen available for plant uptake.
Exam scope and assessment notes
Mapped to the named 0973 section using teaching from the corresponding single-science course. A 0973-specific review of every Core and Supplement objective is still in progress. Written practice is self-checked; it does not demonstrate supervised laboratory competence or award an official Cambridge grade. This qualification reports two grades on the 9–1 scale; confirm the entry route for your zone and exam series.
Before you begin
- Use the food-web pathway and distinguish matter cycling from energy flow.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
What is the main nitrogen-cycle change in nitrification?
What you will learn
- Describe nitrification in the nitrogen cycle
- Distinguish nitrification from fixation and denitrification
Nitrification changes soil nitrogen compounds
Nitrifying microorganisms convert ammonium compounds into nitrate ions through nitrification. In a more detailed account, intermediate nitrogen compounds may be present, but the key syllabus route is ammonium to nitrate.
Nitrification does not take atmospheric N₂ and does not return nitrogen to the air. The process changes nitrogen already in soil compounds. Individual microorganisms do not need to be named for this objective.
Use the correct direction
The cycle route is ammonium compounds → nitrate ions by nitrification. Plants can absorb nitrate ions; other microorganisms can denitrify nitrate back to nitrogen gas. Trace each arrow by checking its starting and ending compounds.
Do not confuse nitrification with nitrogen fixation. Fixation introduces atmospheric nitrogen into compounds; nitrification transforms soil ammonium compounds into nitrates.
Sources for this lesson
Pause and explain
Which role do nitrifying microorganisms perform?
Worked example
Soil contains ammonium ions. A microorganism process produces nitrate ions. Name the process.
Show the worked solution
- The starting form is ammonium.
- The product is nitrate.
Answer The process is nitrification.
Try a topic test
Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Complete the route: ammonium compounds → ____ ions by _____.
Give me a hint
Name the product and process.
Compare my reasoning
- The product taken up by plants is nitrate.
- Ammonium to nitrate is nitrification.
Ammonium compounds → nitrate ions by nitrification.
Look for these in your work
- Product correct
- Process correct
A learner says nitrifying microorganisms return nitrogen to the atmosphere. Correct the statement.
Give me a hint
Identify the product of nitrification.
Compare my reasoning
- Nitrification produces nitrate ions from ammonium compounds.
- Denitrification returns nitrate nitrogen to N₂ gas.
Nitrifying microorganisms convert ammonium compounds into nitrate ions. Denitrification, not nitrification, returns nitrate nitrogen to atmospheric gas.
Look for these in your work
- Nitrification role correct
- Denitrification distinguished
A sample has nitrate ions after soil microorganisms act on ammonium. What process is supported, and what organism-specific claim is unnecessary?
Give me a hint
Use the chemical change and the syllabus wording.
Compare my reasoning
- Ammonium to nitrate supports nitrification.
- The syllabus uses generic microorganism names.
The change supports nitrification. It is unnecessary to name a particular bacterial genus; the syllabus requires the generic microorganism role.
Look for these in your work
- Process inferred from compounds
- Unrequired naming avoided
Common mistakes
- Reversing ammonium and nitrate
- Calling nitrification fixation
- Claiming nitrification directly produces amino acids
What can you explain now?
What is the main nitrogen-cycle change in nitrification?
Compare with the explanation
Ammonium compounds are converted to nitrate ions
This names the direction required.
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Make it stick
State the direction of nitrification and distinguish it from nitrogen fixation and denitrification.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.