10: Chemistry of the Environment

Tests for Water

Anhydrous Cobalt(II) Chloride Test:
Add a few drops of the substance to anhydrous cobalt(Il) chloride, which is blue. The blue paper turns pink if water is present. Anhydrous Copper(II) Sulfate Test: Add a few drops of the substance to anhydrous copper(Il) sulfate, which is a white powder. The white powder turns blue if water is present.

Distilled water

often used in lab experiments instead of tap water because it is very pure and free from these impurities, ensuring more accurate results, as impurities in tap water can interfere with chemical reactions.

If water is pure

test melting point (0C), boiling points (100C)

Beneficial Substances in water

Dissolved oxygen for aquatic life. Some metal compounds provide essential minerals for life.

Harmful substances in water

Some metal compounds are toxic, Some plastics harm aquatic life., Sewage contains harmful microbes which cause disease, Nitrates and phosphates lead to deoxygenation of water and damage to aquatic life.

Treatment of water

Sedimentation, Filtration, Use of Carbon, Chlorination, Clean water

Sedimentation

Water is first allowed to sit in a tank or basin where larger particles and solids settle to the bottom.This process removes most of the suspended solids from the water.’

Filtration

The water is then passed through filters (often made of sand, gravel, or other materials) to remove smaller particles and remaining solids that did not settle during sedimentation.

Use of Carbon

The water is passed through carbon filters to remove tastes, odours, and some organic compounds.

Chlorination

Kills bacteria
Chlorine is added to the water to kill harmful microbes, including bacteria, viruses, and protozoa. This step ensures the water is disinfected and safe for consumption.

Fertilizers

improves plant growth
Nitrogen : Helps plants produce leaves, chlorophyll and proteins, Phosphorus: Helps plants produce flowers, fruits, seeds and roots, Potassium: Helps plants regulate water movement and tolerate stress. Ammonium salts and nitrates enrich soil with nitrogen, which is essential for plant growth

Air

78% nitrogen, 21% oxygen, 1% others

Pollutants

Carbon dioxide, Carbon monoxide and particulates, Methane, Oxides of Nitrogen, Sulphur dioxide

Carbon dioxide

complete combustion of carbon-containing fuels
increased global warming, which leads to climate change

Carbon monoxide

incomplete combustion of carbon-containing fuels
toxic gas

Particulates

incomplete combustion of carbon-containing fuels
increased risk of respiratory problems and cancer

Methane

decomposition of vegetation and waste gases from digestion in animals
increased global warming, which leads to climate change

Oxides of Nitrogen

car engines: nitrogen (from air) and oxygen (from air) react

react due to high temperatures (of engine)
acid rain, photochemical smog and respiratory problems
form in car engines and removed by
catalytic converters, e.g. 2CO + 2NO → 2CO2 + N2

Sulphur dioxide

combustion of fossil fuels which contain sulphur compounds
acid rain
in flue gas desulphurisation, sulphur dioxide reacts with calcium oxide

Global warming

the rise in Earth's temperature caused by greenhouse gases.This leads to changes in weather patterns and other climate effects.

Greenhouse gases

gases in the Earth's atmosphere that trap heat and keep the planet warm. Carbon dioxide and methane are examples of greenhouse gases.

Climate Change

is the rise in Earth's temperature from greenhouse gases.

Acid Rain

is rain made acidic by pollution.

Global warming steps

energy (from the sun) absorbed by Earth's surface

Earth emits or reflects thermal energy

(greenhouse gases) reduces or stops thermal energy loss (into space)

increasing in amount of greenhouse gas results in a higher atmospheric temp

Reducing climate change

Planting trees, Reduction in livestock farming, Decreasing use of fossil fuels, Increasing use of hydrogen and renewable energy, Use of catalytic converters in vehicles (e.g. 2CO + 2NO → 2CO2 + N2), Reducing sulphur dioxide emissions. (In flue gas desulphurisation, sulphur dioxide reacts with calcium oxide.)

Photosynthesis

the process in which plants make glucose and oxygen from carbon dioxide and water.

carbon dioxide + water →(light,chlorophyll) glucose + oxygen

6CO2+ H2O → C6H12O6 + O2