Pearson Edexcel GCSE Combined Science · C8

Fuels and Earth science

50 revision questions with answers for C8 Fuels and Earth science in Pearson Edexcel GCSE Combined Science (spec 1SC0). Practise with flashcards, a topic quiz, a random quiz across the course, 5 crosswords, or read every question and answer below. Not official Pearson material.

All 50 questions and answers

Question 1 · Spec C8.1
What is a hydrocarbon?
Answer:
A compound containing carbon and hydrogen atoms only.
Question 2 · Spec C8.2
What is crude oil?
Answer:
A complex mixture consisting mainly of hydrocarbons, providing fuels and chemical feedstocks.
Question 3 · Spec C8.2
Why is crude oil a finite resource?
Answer:
It forms far more slowly than it is used, so accessible reserves can be depleted.
Question 4 · Spec C8.2
What shapes can carbon skeletons form in crude-oil molecules?
Answer:
Chains and rings; names and structures of particular ring compounds are not required.
Question 5 · Spec C8.2
What is a petrochemical feedstock?
Answer:
A raw material used to make other chemicals and materials rather than simply burned for energy.
Question 6 · Spec C8.3
How does fractional distillation separate crude oil?
Answer:
Heat it to produce vapours, then collect fractions as they condense at different temperatures in the column.
Question 7 · Spec C8.3
How does column temperature vary, and where do small molecules collect?
Answer:
The bottom is hotter and the top cooler; lower-boiling small molecules reach higher parts of the column.
Question 8 · Spec C8.3
Why is a crude-oil fraction still a mixture?
Answer:
It contains several hydrocarbons with similar boiling points rather than one pure compound.
Question 9 · Spec C8.4
What is the listed use of the gases fraction?
Answer:
Domestic heating and cooking.
Question 10 · Spec C8.4
What is the listed use of petrol?
Answer:
Fuel for cars.
Question 11 · Spec C8.4
What is the listed use of kerosene?
Answer:
Fuel for aircraft.
Question 12 · Spec C8.4
What is the listed use of diesel oil?
Answer:
Fuel for some cars and trains.
Question 13 · Spec C8.4
What is the listed use of fuel oil?
Answer:
Fuel for large ships and some power stations.
Question 14 · Spec C8.4
What is bitumen used for?
Answer:
Surfacing roads and roofs.
Question 15 · Spec C8.5
How does increasing hydrocarbon molecule size affect boiling point?
Answer:
Boiling point generally increases.
Question 16 · Spec C8.5
How does increasing hydrocarbon molecule size affect viscosity and ignition?
Answer:
Viscosity increases and the hydrocarbons become harder to ignite.
Question 17 · Spec C8.6
What is a homologous series?
Answer:
Compounds with the same general formula and similar chemical properties, with neighbouring members differing by CH₂.
Question 18 · Spec C8.6
What general formula describes alkanes?
Answer:
CₙH₂ₙ₊₂; physical properties change gradually as molecular size increases.
Question 19 · Spec C8.16
How do saturated alkanes differ from unsaturated alkenes?
Answer:
Alkanes have only single carbon-carbon bonds; alkenes contain a carbon-carbon double bond.
Question 20 · Spec C8.7
What are the products and energy effect of complete hydrocarbon combustion?
Answer:
Carbon dioxide and water form, and energy is transferred to the surroundings.
Question 21 · Spec C8.7
Balance the complete combustion of methane.
Answer:
CH₄ + 2O₂ → CO₂ + 2H₂O.
Question 22 · Spec C8.8
Why can incomplete combustion produce carbon monoxide or carbon?
Answer:
Insufficient oxygen prevents all the carbon being oxidised to carbon dioxide.
Question 23 · Spec C8.9
How does carbon monoxide cause harm?
Answer:
It binds strongly to haemoglobin, reducing the blood's ability to carry oxygen.
Question 24 · Spec C8.10
Why can carbon monoxide from faulty fuel appliances be difficult to notice?
Answer:
It is colourless and odourless, so it can accumulate without obvious warning.
Question 25 · Spec C8.10
What is soot, and why is it a problem?
Answer:
Small carbon particles from incomplete combustion; they can harm breathing and deposit on surfaces.
Question 26 · Spec C8.11
Why can some hydrocarbon fuels release sulfur dioxide?
Answer:
Sulfur impurities burn and react with oxygen.
Question 27 · Spec C8.12
How does sulfur dioxide contribute to acid rain?
Answer:
It dissolves and reacts in rainwater, making it acidic; this can damage aquatic life, plants and buildings.
Question 28 · Spec C8.13
Why do engines produce oxides of nitrogen?
Answer:
High temperatures allow nitrogen and oxygen in the air to react.
Question 29 · Spec C8.14
What is a point-of-use advantage of hydrogen over petrol?
Answer:
Hydrogen combustion forms water rather than carbon dioxide from the fuel.
Question 30 · Spec C8.14
Give two disadvantages of hydrogen as a vehicle fuel.
Answer:
Storage is difficult because of low gas density; it is flammable and its production requires energy.
Question 31 · Spec C8.14
Why does hydrogen's full environmental impact depend on how it is made?
Answer:
Production may use fossil fuels or low-carbon electricity, giving different overall emissions and resource demands.
Question 32 · Spec C8.15
Name the specified non-renewable fuels from crude oil and natural gas.
Answer:
Petrol, kerosene and diesel come from crude oil; methane is a major natural-gas fuel.
Question 33 · Spec C8.16
What is cracking?
Answer:
Breaking larger saturated hydrocarbon molecules into smaller molecules, including alkanes and unsaturated alkenes.
Question 34 · Spec C8.17
Why is cracking useful?
Answer:
Demand for small fuels and alkene feedstocks can exceed their natural supply from crude-oil fractions.
Question 35 · Spec C8.16
Complete C₁₀H₂₂ → C₈H₁₈ + ___.
Answer:
C₂H₄, preserving the total carbon and hydrogen atom numbers.
Question 36 · Spec C8.18
What source of gases formed Earth's early atmosphere in the specified model?
Answer:
Volcanic activity.
Question 37 · Spec C8.19
Describe the proposed early atmosphere.
Answer:
Much carbon dioxide and water vapour, little or no oxygen, and small amounts of other gases.
Question 38 · Spec C8.19
Why is evidence about the earliest atmosphere uncertain?
Answer:
It formed billions of years ago and much direct evidence has been altered or destroyed.
Question 39 · Spec C8.20
How did the oceans form?
Answer:
Earth cooled, causing atmospheric water vapour to condense into liquid water.
Question 40 · Spec C8.21
How did ocean formation reduce atmospheric carbon dioxide?
Answer:
Carbon dioxide dissolved in the newly formed oceans.
Question 41 · Spec C8.22
How did primitive photosynthetic organisms alter the atmosphere?
Answer:
They used carbon dioxide and released oxygen, gradually increasing the oxygen proportion.
Question 42 · Spec C8.23
How is oxygen identified?
Answer:
It relights a glowing splint.
Question 43 · Spec C8.26
Give the approximate modern atmospheric proportions of nitrogen and oxygen.
Answer:
About 78% nitrogen and 21% oxygen, with small amounts of other gases.
Question 44 · Spec C8.24
Name three greenhouse gases in this topic.
Answer:
Carbon dioxide, methane and water vapour.
Question 45 · Spec C8.24
How do greenhouse gases warm Earth?
Answer:
They absorb outgoing infrared radiation and re-emit energy, reducing net energy loss from the surface.
Question 46 · Spec C8.26
Name human activities increasing carbon dioxide and methane.
Answer:
Burning fossil fuels increases carbon dioxide; livestock farming increases methane emissions.
Question 47 · Spec C8.26
Give two possible effects of increased global temperatures.
Answer:
Sea-level rise and changes in rainfall or extreme weather; ecosystems and agriculture can also be affected.
Question 48 · Spec C8.25
What correlation supports a human contribution to climate change?
Answer:
Increased fossil-fuel use and atmospheric carbon dioxide are associated with increased global average temperature, supported by further physical evidence.
Question 49 · Spec C8.25
Why do measurement location and historical accuracy matter in climate evidence?
Answer:
A local record may not represent global conditions, and older measurements may have greater uncertainty.
Question 50 · Spec C8.26
How can climate-change effects be mitigated, and what should decisions consider?
Answer:
Reduce greenhouse emissions and adapt to impacts; compare scale, risks, costs and environmental consequences.

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