The Atmosphere and Environment

Learning Outcomes(a) describe the volume composition of gases present in dry air as being approximately 79%nitrogen, 20% oxygen and the remainder being noble gases (with argon as the mainconstituent) and carbon dioxide

(b) name some common atmospheric pollutants, e.g. carbon monoxide; methane; nitrogenoxides (NO and NO2); ozone; sulfur dioxide; unburned hydrocarbons

Learning Outcomes(c) state the sources of these pollutants as:• (i) carbon monoxide from incomplete combustion of carbon-containing

substances• (ii) nitrogen oxides from lightning activity and internal combustion engines• (iii) sulfur dioxide from volcanoes and combustion of fossil fuels

(d) discuss some of the effects of these pollutants on health and on the environment:• (i) the poisonous nature of carbon monoxide• (ii) the role of nitrogen dioxide and sulfur dioxide in the formation of ‘acid rain’

and its• effects on respiration and buildings

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 %

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 ways

1. 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 rain4 NO2 (g) + 2H2O (l) + O2 (g) 4HNO3 (aq)

Forming acid rainCO2 (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