Air and Water

Composition of Air

Air is a mixture of mainly oxygen and nitrogen, with very small amounts of other gases such as argon, carbon dioxide, and water vapour.

Fractional Distillation of Liquefied Air

Fractional distillation is used to separate the main components of air.
This process involves first cooling air until it liquefies and then gradually heating this liquid air.
Different components will boil off at different temperatures, starting with nitrogen, then oxygen, then argon.

Non-Polluting Gases

Oxygen is vital for respiration in most life on Earth.
Nitrogen is used by plants to make proteins.
Argon is used in light bulbs because it does not react with the filament, even at high temperatures.

Polluting Gases

Carbon dioxide is a greenhouse gas, and excess amounts in the air can cause global warming.
Sulphur dioxide is a toxic gas, and can create acid rain which harms living things and buildings.
Nitrogen oxides are also toxic and can create acid rain, they are produced by burning fossil fuels.
Carbon monoxide is a poisonous gas produced from the incomplete combustion of carbon-containing fuels.

Water Pollutants

Microorganisms in water can cause diseases if the water is not treated adequately.
Nutrients such as nitrates and phosphates can lead to eutrophication, reducing water quality.
Heavy metals can be toxic and build up in organisms.
Organic matter can decrease oxygen levels in water, harming aquatic life.

Water Purification

Water can be purified by filtration to remove solid particles, then by chlorination to kill microorganisms.

Water Hardness

Hard water contains dissolved minerals that can build up in plumbing, prevent soap from lathering, and are bad for certain industrial processes.
Hard water can be softened by adding a water softener or by using an ion-exchange resin.

Properties of Water

The solvent properties of water make it essential for life as it is used to transport substances around an organism.
Water’s high heat capacity helps regulate temperatures in organisms and the environment.
Cohesive properties of water allow it to flow, making it ideal for transport of substances.
Its maximal density at 4 degrees Celsius, unlike most substances, ensures oceans and lakes don’t freeze solid, providing a stable environment for aquatic life.