SChem_C17.ppt

(1)

CHAPTER

17

The Atmosphere and

Environment

(2)

17.1 Composition of Air

17.2 Air Pollution

Chapter 17 The Atmosphere and Environment

(3)

Learning Outcome

• describe the composition by volume of gases present in dry air.

At the end of this section, you should be able to:

(4)

Pie Chart Showing Composition of Air

Composition of air varies with time and place.

17.1 Composition of Air

(5)

Air

Liquid air

Nitrogen

(b.p. −196oC)

Argon

(b.p. −186oC)

Oxygen

(b.p. −183oC) cooling and

compression _distillationfractional

(6)

6

(7)

Learning Outcomes

• name some common air pollutants and state their sources;

• describe the effects of some air pollutants on health and the environment.

At the end of this section, you should be able to:

(8)

Air pollution

is a condition in which air contains a

high concentration

of chemicals that may

harm

(9)

Air pollution is caused by

particulates

(like soot/dust)

and

harmful gases

in the air.

Main pollutants include: •CO,

•SO₂ •NO

•Unburnt hydrocarbons •Ozone

(10)

• Incomplete combustion of fossil fuels in power plants, factories or combustion engines of vehicles due to lack of oxygen

17.2 Air Pollution

Sources of Carbon Monoxide

4CH₄(g) + 5O₂(g) →

2CO(g) + 8H₂O(g) + 2C(s) + heat energy

(11)

• Poisonous as it combines irreversibly with

haemoglobin in blood to form carboxyhaemoglobin

– Reduces ability of haemoglobin to carry oxygen to different parts of the body

• Causes

– headaches, fatigue, breathing difficulties – heart damage, loss of consciousness

– DEATH as body tissues do not receive oxygen for respiration

17.2 Air Pollution

(12)

• Combustion of fossil fuels which contain sulfur

impurities (e.g. coal) in power stations and factories:

S(s) + O₂(g)→ SO₂(g)

17.2 Air Pollution

• Volcanic eruptions

12

(13)

17.2 Air Pollution

• Causes

– eye and lung irritation

– inflammation of the lungs (bronchitis) at high levels

– breathing difficulties

• Combines with oxygen and rainwater to form

acid rain, which corrodes buildings and harms aquatic life and plants

(14)

• Internal combustion engines • Lightning activity

At high temperatures, nitrogen combines with oxygen to form

nitrogen monoxide (NO): N₂(g) + O₂(g) → 2NO(g)

NO reacts with oxygen to

produce nitrogen dioxide (NO₂): 2NO(g) + O₂(g) → 2NO₂(g)

Sources of Oxides of Nitrogen (NO, NO2)

17.2 Air Pollution

colourless gas

brown

(15)

17.2 Air Pollution

Effects of Oxides of Nitrogen (NO, NO2)

• Causes

– eye and lung irritation

– inflammation of the lungs (bronchitis) at high levels

– breathing difficulties

• Combines with oxygen and rainwater to form

(16)

•Unburnt hydrocarbons

– Released in car exhaust and chemical plants

•Methane

– Produced when plant and animal matter decay

– Released by the digestion of food in sheep and cows – Produced when rubbish in landfills decay

•Ozone (at ground level)

– Formed when nitrogen dioxide in the air reacts with unburnt hydrocarbons in sunlight

17.2 Air Pollution

Sources of Other Air Pollutants

(17)

Unburnt Hydrocarbons

Source:

•Produced by car exhausts

Effect:

•Known to

react with oxides of nitrogen in the

(18)

Methane Gas

Sources:

•_{Released by}_bacteria _during_{decomposition/decay} _{of plants}

and animal matter

•_{Released during}_digestion_{of food in sheep and cows} •_{Rice growing}

(19)

Methane Gas

Effects:

•_{Small amounts are harmless.}

•_{In large amounts, methane and other gases}_{traps heat}_{from the}

(20)

Ozone

• Ozone (O₃) is a form of oxygen. A layer of ozone surrounds the earth at a high altitude

• _It_protects _{the planet from}

excess UV radiation from the sun

• _{At ground level, ozone can}

(21)

Ozone

Source:

•

Sunlight acting on unburnt hydrocarbons and nitrogen

dioxide from car exhausts

Effect:

(22)

2H₂SO₃(aq) + O₂(g) → 2H₂SO₄(aq)

4NO₂(g) + O₂(g) + 2H₂O(l) → 4HNO₃(aq)

17.2 Air Pollution

Acid Rain

Acid rain is formed when sulfur dioxide and nitrogen

dioxide react with water in the atmosphere.

SO₂(g) + H₂O(l) → H₂SO₃(aq)

• Sulfur dioxide dissolves in water to form sulfurous acid (H₂SO₃):

• Sulfurous acid is then converted to sulfuric acid:

• Nitrogen dioxide reacts with water and oxygen to form nitric acid:

(23)

(24)

A. Formation of acid rain

C. Effects of acid rain on plants D. Acid rain damages statues/buildings B. Acid rain damages aquatic life such as fish

(25)

Acidifies lakes and streams

Harmful Effects of Acid Rain

Aquatic plants and animals die.

Plants wither and die. Leaches nutrients

from soil

Reacts with metals and carbonates

Marble and limestone

buildings/statues corrode; metal bridges are damaged.

17.2 Air Pollution

(26)

Concept Map

Chapter 17 The Atmosphere and Environment

(27)

(28)

Chapter 8

28

Acknowledgements

Wikimedia Commons | Public Domain

CC BY-SA3.0

(http://creativecommons.org/licenses/by/3.0/deed.en) The URLs are valid as at 15 October 2012.