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2cInorganic Chemistry

Gases in the atmosphere — Edexcel Modular - OL (Chemistry) Revision Notes & Topical Questions

5 min read 7 parts Lesson 3 of 8 2 quizzes

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Lesson summary

Gases in the atmosphere Edexcel O Level Modular Chemistry notes: know the approximate percentages by volume of the four most abundant gases in dry air understand how to determine the percentage by volume of oxygen in air using experiments involving the reactions of metals (e.g.

  • Burning element in oxygen
  • Gases in the atmosphere Edexcel O Level Modular Chemistry: what to do next
  • Atmosphere composition
  • Oxygen test
  • Carbon dioxide test
  • Greenhouse gas

Section 1 of 7Process & sequence

  • Burning fossil fuels
  • More CO₂
  • Enhanced greenhouse effect
  • Climate change
Oxygen % experiment
Pass air over hot copper
Volume decreases ~21%
Copper → copper(II) oxide

Section 2 of 7Keep going

Gases in the atmosphere Edexcel O Level Modular Chemistry: what to do next

These Gases in the atmosphere Edexcel O Level Modular Chemistry notes covered the key ideas, worked examples and exam technique for this topic. Check your Gases in the atmosphere Edexcel O Level Modular Chemistry understanding with the practice questions below, then reread any Gases in the atmosphere Edexcel O Level Modular Chemistry point you were unsure about before moving on.

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Practice: Gases in the atmosphere Edexcel O Level Modular Chemistry practice questions
2
Previous lesson: 2b Group 7 (halogens) - chlorine, bromine and iodine — Notes
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Next lesson: 2d Reactivity series — Notes
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Course: Edexcel Modular – OL (chemistry) — all units
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Official syllabus: Pearson Edexcel International GCSEs

Gases in the atmosphere Edexcel O Level Modular Chemistry revision notes

Section 3 of 7Compare

Gases in the atmosphere
Gas% by volumeSourceEffectTestNote
Nitrogen78NaturalUnreactive——
Oxygen21PhotosynthesisSupports combustionRelights glowing splint—
Argon0.9NaturalUnreactive—Noble gas
Carbon dioxide0.04Respiration, combustionGreenhouse effectLimewater milkyRising
Sulfur dioxideTraceBurning fossil fuelsAcid rain—Pollutant

Section 4 of 7Key terms

Section 5 of 7Syllabus checklist

1
know the approximate percentages by volume of the four most abundant gases in dry air understand how to determine the percentage by volume of oxygen in air using experiments involving the reactions of metals (e.g. iron) and non-metals (e.g. phosphorus) with air
2
describe the combustion of elements in oxygen, including magnesium, hydrogen and sulfur
3
describe the formation of carbon dioxide from the thermal decomposition of metal carbonates, including copper(II) carbonate
4
know that carbon dioxide is a greenhouse gas and that increasing amounts in the atmosphere may contribute to climate change
5
practical: determine the approximate percentage by volume of oxygen in air using a metal or a non-metal

Section 6 of 7Command terms

Command terms
Give / State / Name
Recall a fact; one idea per mark.
Define
Give the exact meaning using the specification keywords.
Describe
Give an account of what happens / the pattern in data, quoting values; no reasons needed.
Explain
Give reasons with linked statements (cause → effect). Each linked step is usually a separate marking point.
Suggest
Use knowledge in a new context; more than one answer may be accepted.
Compare
Similarities and differences; each point must refer to both items.
Calculate
Show working; include units; check significant figures. Method marks are given even if the final answer is wrong.
Discuss
Explore the issue from different angles and link the points.
Evaluate / Assess
Weigh strengths and weaknesses and reach a supported judgement.
Deduce
Draw a conclusion from the information given.
Justify
Support a statement/choice with evidence.

Section 7 of 7Exam technique

Keywords the mark scheme looks for in this lesson

Keywords the mark scheme looks for in this lesson
Atmosphere composition · Oxygen test · Carbon dioxide test · Greenhouse gas · Acid rain · Combustion
Learn each definition in the Key words tab exactly; a missing keyword in a definition usually loses the mark.

How to get full marks (examiner guidance)

How to get full marks (examiner guidance)
Use specification keywords exactly (e.g. electronegativity, nucleophile, dynamic equilibrium, activation energy).
Link ideas
Link ideas for “explain” each marking point is usually a cause → consequence step; unlinked facts often score nothing.
Use the information in the question
“discuss/evaluate” answers must use the data provided and match the number of marks.
Convert units carefully (mg → g, cm³ → dm³) and show working for calculations.
Avoid vague words
“it”, “stuff”, “things”, “goes up”, “energy is made”. Name the substance and the process.
Do not extrapolate a graph line beyond the data or to zero unless asked.
Six-mark extended responses are marked on content AND a logical, linked line of reasoning.

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