🌏
Chemistry of the Environment
Class
Chemistry
Type
Reading
In notebook
Water
There are multiple tests for the presence of water:
Test
Type of Test
Positive Result
Add to Anhydrous Cobalt (II) Chloride
Chemical
Turns from blue to pink
Add to Anhydrous Copper (II) Sulphate
Chemical
Turns from white to blue
Test melting point and boiling point
Physical
Melts at 0॰C and boils at 100॰C
While performing experiments, we use distilled water rather then tap water as it
contains lesser impurities.
Water may contain substances such as:
1. Dissolved oxygen
2. Metal compounds
3. Plastics
4. Sewage
5. Harmful microbes
6. Nitrates from fertilisers
7. Phosphates from fertilisers and detergents
Treatment of water for domestic uses:
1. Water pumped through screens to remove solid, insoluble impurities
2. Sedimentation makes small clay pieces stick together that are then removed
Chemistry of the Environment
1
3. Filtration through layers of sand and gravel to remove larger, insoluble debris
4. Carbon added to remove taste and odour
5. Chlorination (chlorine gas bubbled through the water) to kill any
pathogens/microbes
Fertilisers
Fertilisers are substances added to the soil and taken up by plants to increase crop
yield. They contain ammonium salts and nitrates.
NPK → Nitrogen (chlorophyll and protein synthesis, promotes healthy leaves),
Phosphorus (promotes healthy roots), Potassium (promotes growth and healthy
fruits and flowers)
Reaction with any alkali substance (except ammonium) displaces ammonia from its
compound; e.g.:
Sodium Hydroxide + Ammonium Chloride → Sodium Chloride + Ammonia (g)
+ Water
Air Quality and Climate
Composition of Clean air
Clean air primarily
consists of nitrogen
gas (78%) and
oxygen gas (21%).
Secondarily it
consists of noble
gases e.g. Argon
and carbon dioxide
Chemistry of the Environment
2
(together = approx.
1%).n
Impact of Greenhouse Gases
1. Short wavelength radiation from the Sun reaches the Earth's surface
2. Some thermal energy is absorbed and heats oceans/lands
3. Earth radiates some thermal energy as more prolonged wavelength radiation
4. Greenhouse gases absorb some of the infrared radiation and re-emit in all
directions
5. Some infrared radiation comes back to Earth's surface, and this reduces the heat
loss to space and leads to global warming
Air Pollutants and their adverse effects
Pollutant
Source
Negative Impact
Carbon monoxide
[CO]
incomplete combustion of
carbon containing fuels
binds to haemoglobin in blood,
constricting oxygen supply to body
cells (carbon monoxide poisoning)
Carbon dioxide
[CO₂]
complete combustion of
carbon containing fuels
increased global warming leads to
climate change
Methane [CH₄]
decomposition of vegetation
and waste gases from
digestion in animals
increased global warming leads to
climate change
Sulphur dioxide
[SO₂]
combustion of fossil fuels
containing sulphur compounds
causes acid rain
Chemistry of the Environment
3
Pollutant
Source
Negative Impact
Nitrogen oxides
[NO₂, NO₃]
high temperatures that trigger
reaction between N₂ and O₂
(from air)
causes respiratory problems and
photochemical smog, contributes to
acid rain
Lead compounds
combustion of leaded fuels
damages brain and nerve cells in
young children
Strategies to reduce the effects of Environmental
Issues
Climate change: planting trees, reducing livestock farming, decreasing the use of
fossil fuels, increasing the use of hydrogen and renewable energy (e.g. wind,
solar, geothermal)
Acid rain: use of catalytic converters in vehicles, reducing emissions of sulphur
dioxide by using low-sulphur fuels and flue gas desulphurisation with calcium
oxide
Photosynthesis
Photosynthesis is the reaction between carbon dioxide and water to produce
glucose and oxygen in the presence of chlorophyll and using energy from light.
💡
Word equation:
Carbon Dioxide + Water → Chlorophyll + Oxygen
(Balanced) Symbol Equation:
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
Chemistry of the Environment
4