The atmosphere and Environment

The Atmosphere and the Environment

Composition of air

1. Presentation in graphs/charts

2. Experiments which show composition of air

Air Pollution

Identity of air pollutants

Sources/how they are formed

Equations

Effects

Equations

Acid rain

Composition of air

• Air is a mixture of several gases, both elements and compounds.

• Its composition varies from time to time.

Gas Composition by volume

Nitrogen 79 %

Oxygen 20 %

Noble gas (mostly Argon)+ Carbon Dioxide

1 %

Representations of air composition

1. Only oxygen gas will react with copper upon heating.

2. We know that oxygen gas only constitute 20% of the volume of air.

3. Thus , after the heated copper reacts with oxygen gas, the volume of air will decrease by 20% ( 80% of the volume of air is left. )

4. Thus, the volume of air left in syringe B is 80% x 200cm3 = 160cm3

Answer: Option C

Air pollution

• Definition : the pollution caused by chemicals in the air that can harm living things or damage non-living things

• Example - – Ozone , O3

– Unburnt hydrocarbons– Carbon monoxide , CO– Oxides of nitrogen , NO , NO2

– Sulfur dioxide , SO2

Carbon monoxide

• Properties – Poisonous– Colourless– Odourless

• Source – Incomplete combustion of carbon-containing fuels ; i.e.

incomplete combustion of petrol in car engines

• Effects – CO reacts with haemoglobin in blood to form

carboxyhaemoglobin. As a result, it cannot transport oxygen to the rest of the body.

– Headaches, fatigue, breathing difficulties and even death

3 Dimensional model of haemoglobin

Oxides of nitrogen

• Produced in 2 ways1. Due to high temperature in a car engine, the nitrogen

present combines with oxygen to form nitrogen monoxide (NO) or nitric oxide, a colourless gas.

N2 (g) + O2 (g) 2NO (g)

NO (g ) + O2 (g) 2NO2 (g)

2. Heat energy released when lightning strikes. This causes the nitrogen and oxygen to react to form NO and NO2.

Sulfur dioxide

• Source – Combustion of fossil fuel e.g. coal , crude oil and

natural gas – Volcano eruptions

• Fossil fuel contains sulfur

S (s) + O2 (g) SO2 (g)

Effects from sulfur dioxide and oxides of nitrogen

• Eye irritation• Lung irritation breathing difficulties• Inflammation of lungs bronchitis• Both gasses form acid rain– Acid rain destroys buildings, plants and aquatic

life– pH of acid rain ~ 4

Forming acid rain

• SO2 (g ) + H2O (l) H2SO3 (aq)

Sulfur dioxide sulfurous acid

H2SO3 then slowly reacts with oxygen to form sulfuric acid, H2SO4

Forming acid rain

4 NO2 (g) + 2H2O (l) + O2 (g) 4HNO3 (aq)

Forming acid rain

CO2 (g) + H2O (l) H2CO3 (aq)

Effects of acid rain

• Acid reacts with metals, carbonates in marble and limestone .– Recall acids chapter!!!– This affects metal bridges and stone buildings

• Makes lakes and rivers acidic kill fish and other aquatic life.

• Leaches (dissolves out) important nutrients from the soil plants are destroyed