📋 Structured Questions
These questions test key concepts from Topic 9. Attempt each question on paper, then click "Show Mark Scheme" to check your answer.
Question 1: Production of Nitrogen Oxides
2 marksIn the future, gas central heating boilers may burn hydrogen rather than natural gas.
(a) Explain how oxides of nitrogen are produced when burning fuels. [2]
Show Mark Scheme
- At high temperatures [1]
- Nitrogen (from the air) and oxygen (from the air) react [1]
Question 2: Incomplete Combustion
2 marksNatural gas is mainly methane. When methane burns it can produce both carbon monoxide and carbon dioxide.
(a) Explain the process by which carbon monoxide can be produced when methane is burned. [2]
Show Mark Scheme
- Not enough oxygen (accept "not enough air" or "limited supply of oxygen") [1]
- (So) incomplete combustion occurs [1]
Question 3: Population Growth & Methane
2 marksIn the past 50 years, there has been an increase in the world population, the concentration of methane in the atmosphere, and the mean temperature of the atmosphere.
(a) Explain why the increase in world population may have caused the increase in the concentration of methane in the atmosphere. [2]
Show Mark Scheme
- More food is required (due to increased population) [1]
- More methane-producing food production (e.g. more cattle farming / rice paddies) [1]
Alternative route: More waste is produced → which produces more methane on decomposition.
Question 4: Formation of Natural Gas
3 marksA graph shows how the percentages of gases in the Earth's atmosphere may have changed since the atmosphere was formed. Natural gas is a fossil fuel.
(a) Describe how deposits of natural gas were formed. [3]
Show Mark Scheme
- Plankton / tiny marine organisms died [1]
- Covered by sediments / buried in anaerobic conditions [1]
- Subjected to high temperature and high pressure (over millions of years) [1]
Question 5: The Greenhouse Effect
3 marksTitan is a moon of the planet Saturn. Saturn has other moons that have no atmosphere. Titan is warmer than the other moons of Saturn because its atmosphere contains the greenhouse gas methane.
(a) Explain how this greenhouse gas keeps Titan warmer than the other moons of Saturn. [3]
Show Mark Scheme
- (Methane) allows short wavelength radiation to pass through (from the Sun) [1]
- (Which is) re-emitted from the surface as longer wavelength radiation [1]
- (Which is) absorbed by methane in the atmosphere [1]
Question 6: Sulfur Dioxide & Limestone Erosion
4 marksFossil fuels are burned in car engines. A limestone carving has been damaged by atmospheric pollution. It has been eroded where the limestone has reacted with atmospheric pollutants.
(a) Explain how reducing the amount of sulfur in fossil fuels reduces the erosion of limestone. [4]
Show Mark Scheme
- Sulfur reacts with oxygen to form sulfur dioxide [1]
- (So) less sulfur dioxide is emitted [1]
- (So) there is less acid rain [1]
- (So) less limestone reacts with acid rain [1]
Question 7: Changes to the Earth's Atmosphere ⭐ Extended Response
6 marksThe Earth's early atmosphere was very different from the atmosphere today.
(a) Describe and explain how the surface of the early Earth and its atmosphere have changed to form the Earth's atmosphere today. [6]
Show Mark Scheme
Level 3 (5–6 marks): Changes to both the Earth's surface and atmospheric composition are identified, detailed, and logically linked to their causes.
Level 2 (3–4 marks): Some changes to the atmosphere identified with attempts to explain causes, but may omit significant processes (e.g. mentions photosynthesis but forgets ocean formation).
Level 1 (1–2 marks): Simple statements about early vs. modern atmosphere (e.g. "there is more oxygen now" or "volcanoes formed it").
Indicative content:
- As Earth cooled, water vapour condensed to form the oceans
- CO₂ decrease: CO₂ dissolved in the newly formed oceans
- Carbonates precipitated from oceans to form sedimentary rocks, locking up carbon
- Algae and green plants evolved and absorbed CO₂ for photosynthesis
- Marine organisms used carbonates for shells/skeletons → eventually formed fossil fuels
- O₂ increase: algae and plants produced oxygen as a byproduct of photosynthesis
Question 8: Practical Skills — Testing for Atmospheric Gases 🔬
4 marksA student collects samples of four different gases and needs to identify them using standard laboratory tests.
(a) Describe the test and expected positive result for each of the following gases: oxygen, carbon dioxide, hydrogen, and chlorine. [4]
Show Mark Scheme
- Oxygen: insert a glowing splint → it relights [1]
- Carbon dioxide: bubble through limewater → turns milky/cloudy [1]
- Hydrogen: hold a lit splint near the gas → produces a squeaky pop [1]
- Chlorine: hold damp litmus paper near the gas → bleaches it white [1]