Chemistry of the environment.

why is distilled water is used in practical chemistry rather than tap water

it has fewer chemical impurities

State that water from natural sources may contain substances, including

dissolved oxygen

metal compounds

plastics

sewage

harmful microbes

nitrates from fertilizers

phosphates from fertilisers and detergents

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beneficial substances:

dissolved oxygen for aquatic life

some metal compounds provide essential minerals for life

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harmful:

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 removes large, dense particles and insoluble solids. Water is pumped into sedimentation tanks and allowed to stand for a few hours

  Mud, sand and other particles will fall to the bottom of the tank due to gravity and form a layer of sediment.

  Filtration is done to remove insoluble solids and small particles. The water is then filtered through sand and gravel to remove smaller particles

• Carbon is also added into filtered water to remove taste and odour

• The chlorination process adds chlorine gas bubbled into the water to kill bacteria and other microbes

ammonium salts and nitrates are used

fertilizers

use of NPK fertilisers

provide the elements nitrogen, phosphorus and potassium for improved plant growth

composition of clean, dry air

78% nitrogen

21% oxygen

and the remainder as a mixture of noble gases and carbon dioxide, CO2

source of air pollutants

* CO2 from the complete combustion of carbon-containing fuels
* carbon monoxide and particulates - incomplete combustion of carbon-containing fuels
* methane - decomposition of vegetation and waste gases from digestion in animals
* oxides of nitrogen - nitrogen reacting with oxygen in car engines at high temperatures
* sulfur dioxide - combustion of fossil fuels which contain sulfur compounds

adverse effects of pollutants

CO2 -: higher levels of carbon dioxide leading to increased global warming, which leads to climate change

carbon monoxide - toxic gas

particulates - increased risk of respiratory diseases and cancer

methane - higher levels of methane leading to increased global warming, which leads to climate change

oxides of nitrogen - acid rain, photochemical smog and respiratory problems

sulfur dioxide - acid rain. acid rain damages trees and limestone buildings. acidifies soil, and damages metal works.

how do greenhouse gases affect global warming

• (insert gas) is a greenhouse gas

• enhances greenhouse effect

• heat and infra-red/long-wavelength radiation

• is absorbed by greenhouse gases

• travels back to the surface

• heat cannot leave the atmosphere into outer space

reduce climate change

* plant trees
* reduction in livestock farming
* decreasing use of fossil fuels
* increasing use of hydrogen and renewable energy

reduce acid rain

* use catalytic converter in vehicles
* reducing emissions of sulfur dioxide by using low-sulfur fuels
* flue gas desulfurization with calcium oxide

photosynthesis

the reaction between carbon dioxide and water to produce glucose and oxygen in the presence of chlorophyll and using energy from light.

6CO2 + 6H2O → C6H12O6 + 6O2

catalytic converters

• Combine CO with oxygen to convert it to carbon dioxide.

• 2CO + O2 → 2CO2

• Reduce oxides of nitrogen to nitrogen:

  2NO → N2 + O2

• React CO with NO to produce CO2 and N2

• 2CO + 2NO → 2CO2 + N2