IGCSE Chemistry
2026 - 2028
Syllabus Checklist ✅
Topic 16: Chemistry of the Environment
Water
Describe chemical tests for water using anhydrous cobalt(II) chloride
and anhydrous copper(II) sulfate
Test for the purity of water
using melting point
and boiling point
Explain why distilled water
is used in practical chemistry rather than tap water
(fewer impurities)
State that natural water may contain: dissolved oxygen
, metal compounds
, plastics
, sewage
, harmful microbes
, nitrates
and phosphates
Some substances are beneficial: (a) dissolved oxygen
for aquatic life (b) some metal compounds
provide essential minerals
Some substances are harmful: (a) toxic metal compounds
(b) some plastics
harm aquatic life (c) sewage
contains microbes causing disease (d) nitrates
and phosphates
cause deoxygenation of water
Describe treatment of domestic water: (a) sedimentation & filtration
(b) carbon
to remove tastes/odours (c) chlorination
to kill microbes
Fertilisers
State that ammonium salts
and nitrates
are used as fertilisers
Describe the use of NPK fertilisers
to supply nitrogen
, phosphorus
and potassium
Air Quality and Climate
State composition of clean, dry air: ~ 78% N₂
, 21% O₂
, remainder noble gases and CO₂
Sources of pollutants: (a) CO₂
from complete combustion (b) CO
& particulates
from incomplete combustion (c) CH₄
from decomposition & animal digestion (d) NOₓ
from car engines (e) SO₂
from S-containing fuels
Adverse effects: (a) CO₂
→ global warming → climate change (b) CO
toxic (c) particulates
→ respiratory issues/cancer (d) CH₄
→ global warming (e) NOₓ
→ acid rain, photochemical smog, respiratory problems (f) SO₂
→ acid rain
Explain greenhouse effect of CO₂
and CH₄
: (a) absorption/reflect/emit thermal energy
(b) reduce thermal energy loss to space
Strategies to reduce impacts: (a) climate change
– plant trees, reduce livestock farming, decrease fossil fuels, increase hydrogen
& renewables
(b) acid rain
– catalytic converters, low-sulfur fuels, flue gas desulfurisation
with CaO
Photosynthesis
Describe photosynthesis
as CO₂
+ H₂O
→ glucose
+ O₂
in presence of chlorophyll
and light energy
State the word equation
: carbon dioxide + water → glucose + oxygen
State the symbol equation
: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
Explain NOₓ
formation in car engines and removal by catalytic converters
, e.g. 2CO + 2NO → 2CO₂ + N₂
Corrosion of Metals
State conditions for rusting
of iron/steel to form hydrated iron(III) oxide
(oxygen and water)
State barrier methods: painting
, greasing
, plastic coating
Describe how barrier methods prevent rusting by excluding oxygen
or water
Describe galvanising
with zinc
as a barrier and sacrificial protection
Explain sacrificial protection
using the reactivity series
and electron loss
(zinc preferentially oxidised)
