Air and air quality
Cambridge IGCSE Chemistry (0620) · Unit 10: Chemistry of the environment · 10 flashcards
Air and air quality is topic 10.2 in the Cambridge IGCSE Chemistry (0620) syllabus , positioned in Unit 10 — Chemistry of the environment , alongside Water and Carbon dioxide and methane. In one line: Ammonium salts and nitrates are primarily used as fertilisers. They provide essential nitrogen to the soil, which is crucial for healthy plant growth and development.
This topic is examined in Paper 1 (multiple-choice) and Papers 3/4 (theory), plus Paper 5 or Paper 6 (practical / alternative to practical). Past papers from 2022 to 2025 show this topic across undefined questions worth 206 marks (around 3.2% of all Chemistry marks in those years).
The deck below contains 10 flashcards — 3 definitions, 4 key concepts and 3 identification cards — covering the precise wording mark schemes reward. Use the 3 definition cards to lock down command-word answers (define, state), then move on to the concept and application cards to handle explain, describe and compare questions.
Ammonium salts and nitrates primarily used for in agriculture
Ammonium salts and nitrates are primarily used as fertilisers. They provide essential nitrogen to the soil, which is crucial for healthy plant growth and development.
What the Cambridge 0620 syllabus says
Official 2026-2028 specThese are the exact learning objectives Cambridge sets for this topic. Match the command word (Describe, Explain, State, etc.) in your answer to score full marks.
- State State that ammonium salts and nitrates are used as fertilisers
- Describe Describe the use of NPK fertilisers to provide the elements nitrogen, phosphorus and potassium for improved plant growth
What are ammonium salts and nitrates primarily used for in agriculture?
Ammonium salts and nitrates are primarily used as fertilisers. They provide essential nitrogen to the soil, which is crucial for healthy plant growth and development.
What are NPK fertilisers and what do they provide?
NPK fertilisers contain the elements nitrogen (N), phosphorus (P), and potassium (K). These elements are vital for improved plant growth, with nitrogen promoting leaf growth, phosphorus supporting root development, and potassium aiding overall plant health.
Under what conditions do nitrogen and oxygen react in the air to form oxides of nitrogen in a car engine?
Nitrogen and oxygen from the air react at high temperatures inside the car engine. This extreme heat provides the energy necessary to break the strong bonds in nitrogen and oxygen molecules, allowing them to combine and form nitrogen oxides.
What negative environmental impact can nitrogen oxides contribute to?
Nitrogen oxides contribute to acid rain. They dissolve in atmospheric moisture, forming acids that fall as precipitation, harming ecosystems and damaging infrastructure.
What is thermal decomposition?
Thermal decomposition is the breakdown of a chemical substance by heating it. A single compound breaks down into two or more simpler substances because of heat.
Describe the chemical test to identify ammonium ions (NH₄⁺). Include the reagents used.
To test for ammonium ions, add aqueous sodium hydroxide (NaOH) to the sample and gently heat the mixture. Ammonium ions react with hydroxide ions to release ammonia gas.
What observation indicates a positive result when testing for ammonium ions?
A positive result for the ammonium ion test is when the damp red litmus paper turns blue. This indicates the presence of alkaline ammonia gas, confirming the presence of ammonium ions.
Why are unburnt hydrocarbons in car exhaust harmful?
Unburnt hydrocarbons contribute to smog and can have carcinogenic effects. They react with other pollutants in the presence of sunlight to form ground-level ozone, a major component of smog.
What is the purpose of a catalytic converter in a car?
A catalytic converter reduces pollution from car exhaust. It converts harmful pollutants like carbon monoxide (CO), nitrogen oxides (NOx), and unburnt hydrocarbons into less harmful substances like carbon dioxide (CO2), nitrogen (N2), and water (H2O).
Besides sodium hydroxide, what *other* test can be used alongside it when testing for ammonium ions?
Sodium hydroxide is used to release ammonia gas from ammonium compounds, which can then be tested using damp red litmus paper (it turns blue). If a carbonate impurity is present, limewater (calcium hydroxide solution) can be used to test for any evolved carbon dioxide gas, which will turn the limewater cloudy.
Key Questions: Air and air quality
What are ammonium salts and nitrates primarily used for in agriculture?
Ammonium salts and nitrates are primarily used as fertilisers. They provide essential nitrogen to the soil, which is crucial for healthy plant growth and development.
What are NPK fertilisers and what do they provide?
NPK fertilisers contain the elements nitrogen (N), phosphorus (P), and potassium (K). These elements are vital for improved plant growth, with nitrogen promoting leaf growth, phosphorus supporting root development, and potassium aiding overall plant health.
What is thermal decomposition?
Thermal decomposition is the breakdown of a chemical substance by heating it. A single compound breaks down into two or more simpler substances because of heat.
Tips to avoid common mistakes in Air and air quality
- ● When describing reactions, record observations separately for dropwise addition versus excess addition; if a precipitate appears and vanishes, report both stages distinctly.
- ● In qualitative analysis, state 'precipitate forms' AND 'precipitate dissolves' if you observe both during excess addition.
- ● Make a table of common ions (Cu2+, Fe2+, Cl-, CO32-) with reagents (NaOH, limewater, acidified barium nitrate) and expected observations (blue precipitate, bubbles, white precipitate).
- ● Memorize the qualitative tests for common ions: reagents, conditions, and observations.
- ● Memorize the key qualitative tests, including what reagents to use, and what colours/precipitates to expect, such as zinc ions plus ammonia.
More topics in Unit 10 — Chemistry of the environment
Air and air quality sits alongside these Chemistry decks in the same syllabus unit. Each uses the same spaced-repetition system, so progress in one informs the next.
Cambridge syllabus keywords to use in your answers
These are the official Cambridge 0620 terms tagged to this section. Mark schemes credit responses that use the exact term — weave them into your answers verbatim rather than paraphrasing.
Key terms covered in this Air and air quality deck
Every term below is defined in the flashcards above. Use the list as a quick recall test before your exam — if you can't define one of these in your own words, flip back to that card.
Related Chemistry guides
Long-read articles that go beyond the deck — cover the whole subject's common mistakes, high-yield content and revision pacing.
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