Air Quality
What are the two main gases in the air by percentage?
Nitrogen (~78%) and Oxygen (~21%)
Name the type of polymerisation that produces only the polymer as the product — and explain why this makes the polymer non-biodegradable.
Addition polymerisation.
It uses monomers with C=C double bonds which join together, leaving only strong C–C single bonds and no side products.
The strong carbon backbone is chemically unreactive and lacks functional groups for enzymes to attack, so it’s non-biodegradable.
What colour change happens with anhydrous copper(II) sulfate when testing for water?
Name two human activities that increase atmospheric CH4.
1️⃣ Livestock farming:
Animals like cows, sheep, and goats produce methane during their digestive processes (enteric fermentation).
2️⃣ Landfills and waste disposal:
Decomposition of organic waste in landfills by bacteria releases methane as a by-product.
Which ions in water sources can cause eutrophication?State their sources
Nitrates and phosphates.
Nitrates:
Runoff from agricultural fertilisers (e.g., ammonium nitrate).
Waste from sewage.
Phosphates:
From fertilisers used on farmland.
Detergents that contain phosphate compounds.
Sewage discharge.
Which gas is produced during incomplete combustion that can bind to haemoglobin? Give the balanced equation of the incomplete combustion when methane is burned.
Carbon monoxide. CH4 + 3/2 O2 → CO + 2H2O.
Why does poly(vinyl chloride) (PVC) release harmful gases when burned? Name one gas produced and its environmental effect.
PVC contains chlorine atoms. When burned, it can release hydrogen chloride gas (HCl).
This gas is toxic and corrosive; it contributes to acid rain when it dissolves in atmospheric moisture.
Name the 3 main stages in water treatment.
Sedimentation, Filtration (carbon), Chlorination
Why is methane considered more potent than CO₂ as a greenhouse gas?
Methane traps more heat per molecule than CO₂.
Why does acid rain damage statues made of calcium carbonate? Write a word or symbol equation to show what happens.
Acid rain (contains H₂SO₄) reacts with calcium carbonate (CaCO₃) to form calcium sulfate, water, and carbon dioxide:
CaCO₃ + H₂SO₄ → CaSO₄ + H₂O + CO₂
Which pollutants contribute to acid rain, and name their sources?
Oxides of nitrogen (car engines, lightning) & sulfur dioxide (burning fossil fuels)
Explain why microplastics are a growing problem in oceans, even though plastics are chemically unreactive.
Plastics break down physically into tiny particles called microplastics due to sunlight and wave action but don’t decompose chemically.
These microplastics can be eaten by marine animals, blocking their digestive systems or introducing toxins into the food chain.
Because plastics are chemically stable, they persist for decades.
How does impurity affect boiling and melting points of water?
Impurities raise the boiling point above 100 °C and lower the melting point below 0 °C
Name TWO ways humans can reduce atmospheric methane, and explain ONE advantage and ONE limitation for each method.
1) Reduce livestock farming: + Cuts methane from digestion; – May impact food supply/economy.
2) Better landfill management: + Capture methane for fuel (biogas); – Expensive to build and maintain collection systems.
What is flue gas desulfurisation, why is it used in power stations, and name the main chemical used to remove sulfur dioxide?
Flue gas desulfurisation is a process that removes sulfur dioxide (SO₂) from waste gases produced by burning fossil fuels.
It’s used to reduce acid rain caused by SO₂ emissions from power stations.
The main chemicals used are calcium oxide (lime) or calcium carbonate, which react with sulfur dioxide to form calcium sulfate.
Particulates are a form of air pollutant produced by certain combustion processes.
Explain how particulates are formed (100), name one source(100), and describe TWO harmful effects(200) they have on human health or the environment
Particulates are tiny solid carbon particles (soot) formed during incomplete combustion of carbon-containing fuels when there is insufficient oxygen.
One source is car engines burning petrol or diesel incompletely.
Harmful effects:
Can cause respiratory problems and worsen conditions like asthma.
Can contribute to cancer if inhaled over long periods.
Explain why many addition polymers are non-biodegradable and how this chemical property creates problems for landfill sites.
Addition polymers are made of long chains with strong carbon-carbon bonds and no functional groups that bacteria or enzymes can easily break down.
Because they’re chemically unreactive, micro-organisms cannot decompose them.
This means waste plastics accumulate in landfill, taking up space and lasting for hundreds of years.
Explain why cobalt(II) chloride paper changes colour when exposed to water vapour — include the reaction that happens.
The anhydrous cobalt(II) chloride reacts with water to form hydrated cobalt(II) chloride:
CoCl₂(s) + 6H₂O(l) ⇌ CoCl₂·6H₂O(s).
It changes from blue (anhydrous) to pink (hydrated).
A country plans to reduce its total greenhouse gas emissions by switching all power stations to natural gas instead of coal.
(a) Explain how this change would affect CO₂ and CH₄ emissions.
(b) State ONE benefit and ONE hidden risk of using more natural gas for climate change.
(a) Natural gas combustion produces less CO₂ per unit of energy than coal because it contains more hydrogen and less carbon — so CO₂ emissions decrease. But extraction and transport of natural gas can release methane (CH₄) through leaks, which is a more potent greenhouse gas.
(b) Benefit: Reduces CO₂ emissions compared to coal, so it helps lower the main greenhouse gas.
Hidden risk: Methane leaks during drilling, storage, and pipelines can partly cancel out CO₂ savings because CH₄ traps more heat.
Explain the difference between the greenhouse effect and ozone layer depletion. And state causes of both
The greenhouse effect traps heat with gases like CO₂ and CH₄, warming the Earth. Ozone layer depletion (by CFCs) allows more UV radiation through, increasing skin cancer risk but isn’t the same as warming.
Catalytic converters rely on redox reactions to reduce vehicle emissions.
Explain what “redox” means in this context, describe how the honeycomb structure helps the process,
and write ONE balanced reaction that shows how oxides of nitrogen and carbon monoxide are converted together.
Redox means reduction and oxidation happen simultaneously — harmful gases gain or lose oxygen to become less harmful.
The honeycomb structure inside the converter increases the surface area, making reactions more efficient and faster.
Example reaction:
2NO + 2CO → N₂ + 2CO₂
Compare incineration and landfill disposal for plastic waste:
(a) Give ONE environmental benefit of incineration over landfill.
(b) Explain TWO risks that incinerating plastics can pose.
(a) Benefit: Incineration reduces the volume of waste and can produce useful heat energy (waste-to-energy).
(b) Risks:
Burning plastics can release greenhouse gases like CO₂, contributing to climate change.
Some plastics (like PVC) release toxic gases (e.g., hydrogen chloride) when burned; incomplete combustion can also produce poisonous carbon monoxide.
*A local water supply is tested.
Its melting point is −2 °C.
Its boiling point is 102 °C.
It turns cobalt(II) chloride paper pink.*
(a) What does the melting point and boiling point together suggest about the level of impurities?
(b) Suggest what kind of impurities could cause this effect, and name one natural and one human source.
(c) If this water were used in a lab experiment that requires pure water, what error might it cause?
(d) Explain why simply filtering or boiling this water is not enough to purify it fully.*
(a) The melting point is lower than 0 °C and the boiling point is higher than 100 °C — this means the water contains dissolved impurities that depress the freezing point and elevate the boiling point.
(b) Likely impurities: dissolved salts or ions (e.g., nitrates, metal ions).
Natural source: dissolved minerals from rocks (e.g., calcium or magnesium from limestone).
Human source: nitrates or phosphates from fertilisers, sewage, or detergents.
(c) The impurities could affect chemical reactions, changing concentrations in standard solutions, or contaminating results — leading to inaccurate or non-reproducible data.
(d) Filtration only removes insoluble solids, and boiling removes only microbes — but dissolved ions stay in solution. Full purification would require distillation or deionisation.
Explain why rice paddies contribute to methane emissions, describe one climate-related risk if they expand with a growing population.
Rice paddies are flooded fields with low oxygen — this creates anaerobic conditions where bacteria produce methane as they break down organic matter.
If rice production expands, more CH₄ is released, increasing the enhanced greenhouse effect and risking more climate extremes (e.g., floods, droughts).
Describe the link between melting permafrost and methane emissions.
Why could this create a dangerous positive feedback loop for global warming?
Permafrost (frozen ground) stores large amounts of organic material and trapped methane.
When the climate warms, permafrost melts, releasing trapped methane and allowing decomposition, which produces more methane.
More methane in the atmosphere means more heat is trapped, causing further warming → even more permafrost melts → more methane is released.
This self-reinforcing cycle is called a positive feedback loop, which can accelerate global warming.