Chemistry of the environment

Chemistry of the environment

Process of separating the gases from air

Fractional distillation is required to separate the gases since different components of air have different boiling points.
Air is first liquefied and then liquid air is heated.
Gas with the lowest boiling point moves up the fractional column and vaporize over first

The Carbon Cycle

Remember !
1.Decay and bacterial decomposition of dead animal and plants produce carbon dioxide.
2. Thermal decomposition of metal carbonates produces carbon dioxide.

Green House Gas
Definition: Gases that trap the reflected heat from the earth’s surface are called a greenhouse gas.

Greenhouse gases:
1. CO
2. Water vapor ( H O(g) )
3.Nitrous oxide N O (oxides of nitrogen).
4. Methane (CH )

Green House Effect

1. Solar radiation passes through the atmosphere
2.Some radiation is reflected by the atmosphere back to space.
3. Solar radiation warms the Earth’s surface and some infrared radiation (heat) from the Earth’s surface escapes to space.
4. Greenhouse gases in the atmosphere trap some of the heat and warms the earth’s surface.

Global Warming
Definition: Global warming is the increase in the Earth’s average temperature due to the buildup of greenhouse gases in the atmosphere.

For effects of global warming Point 1 & 3 are found in mark schemes so must be included in the answer.

Effect of Global Warming

1. Climate change
2.A decrease in crop yield worldwide.
3. The melting of large quantities of ice in the north pole and south pole, this will cause the sea level to rise.
4. The rapid evaporation of water from the earth surface. As a result dissolved carbon dioxide enters in the atmosphere which can cause greenhouse effect.

Allotropes : Allotropes are different form of the same element with different physical properties.

Depletion of ozone layer
1.Ozone (O ) is an allotrope of oxygen
2. Color of ozone is pale blue
3. Ozone has a pungent smell.

*CFC (chlorofluorocarbon) is responsible for the depletion of ozone layer

Importance of ozone layer
Some harmful UV radiation from the sun is absorbed by the protective ozone layer, these harmful radiations can cause cancer.

Air pollutants, their sources and their effects.

1. Carbon monoxide.
Source: Incomplete combustion of fuel.
Effects: Toxic gas, it binds strongly with hemoglobin which can cause breathing difficulties and in some cases death.

2.Sulfur dioxide
Source: Combustion of fossil fuels in motor vehicles, power stations and factories.
Effects: Reacts with water in the atmosphere to form acid rain which corrodes buildings, harms aquatic life and plants. It also irritates the eyes, the lungs and cause breathing difficulties.

3.Oxides of nitrogen
Source: Lightning during thunder storms, chemical factories and exhaust fumes of vehicle.
Effect: 1. React with water in atmosphere to form acid rain, which corrodes buildings, harms aquatic lifeand plants.
2. Irritates the eyes, lungs and cause breathing difficulties.

4.Methane Source: decay of plants and animal matter.
Effect: responsible for greenhouse effect that causes global warming.

5.Unburnt Hydrocarbons
Source: Fumes from car exhaust, chemical factories.
Effect: causes cancer.

6.Ozone (O3)
Source: reaction of nitrogen dioxides and unburnt hydrocarbon in the presence of sunlight
Effect: Forms photochemical smog which irritates the eyes, lungs and causes breathing difficulties.

How oxides of nitrogen are formed in car? In car engines the temperature is very high nitrogen (N ) reacts with oxygen ( O ) in air to make Nitrogen monoxide (NO) which in turn reacts with Oxygen in air to make Nitrogen dioxide (NO ) *Nitrogen dioxide is a brown gas.