Chapter 17 Air (Sec 3 E-learning Dec).pptx

Chapter 17:

Learning Outcomes

What is in air?

•

Air is considered a

mixture

. It contains several

different gases.

•

The composition of air is not fixed (i.e. air

consists of different proportion of gases)

depending on the time and place

What does air consist of?

Study the pie chart and fill out blanks in your

How do we separate air?

•

We must first convert air into a liquid. This can be

done by

cooling

and

compressing

the air to form

a liquid

•

Liquid air is then separated by

fractional

distillation

•

The liquid with the lowest boiling point distils

How do we separate air?

• _{Gases with lowest boiling points are found at the top (i.e. they}

Air

Learning Objectives

•

Name some common air pollutants and state

their sources;

What do you think the cartoon is implying?

Air pollution

is a condition in which air contains

a

high concentration

of chemicals that may

Air pollution is caused by

solid

particles

(like soot/dust) and

harmful gases

in the air.

Main pollutants include:

• CO,

• SO2

• _NO

• Unburnt hydrocarbons

• Ozone

Carbon Monoxide

Source:

• _{Due to incomplete combustion of hydrocarbons and fuels in}

Carbon Monoxide

Effect:

• _{Colourless, odourless and}

poisonous gas

• _{It combines with haemoglobin}

in our red blood cells and

prevents oxygen from binding

• _{CO poisoning reduces oxygen}

Carbon Monoxide

Control:

• _{Design more efficient engines in motor vehicles}

• _{Install catalytic converters in vehicles to reduce CO emissions} • _{Reduce the number of cars on the roads}

Sulfur Dioxide

Source:

• _{Combustion of fuels containing sulfur impurities (e.g.}

factories, cars)

• Coal contains some sulfur impurities

Sulfur Dioxide

Effects:

•

Health issues:

– _{Eye irritation}

– _{Bronchitis (inflammation of lungs) and breathing}

difficulties

•

Acid rain

Sulfur Dioxide

Control:

•

Use fuels which contain

lesser

sulfur impurities

•

Prevent SO

release by

spraying exhaust pipes with

alkalis

and water to absorb

the gas

– _{Alkalis helps neutralise the}

acid Coal contains high sulfur impurities. Combustion of coal increases the

Oxides of Nitrogen

Source

•

Released from

car exhausts

– _{At high temperatures, the nitrogen in the air combines with}

oxygen to produce oxides of nitrogen (e.g. NO and NO₂)

•

Produced during

lightning

strikes

(due to very high

Oxides of Nitrogen

Effect

•

Nitrogen dioxide (NO

) combines with water to form

nitric acid (HNO

)

which then forms

acid rain

•

Oxides of nitrogen

corrode metal surfaces

Oxides of Nitrogen

Control

•

Prevent release of oxides of nitrogen by

neutralising

the

gases with

alkalis

•

Install

catalytic converters

in vehicles to reduce release

of oxides of nitrogen

•

Design and use engines which produce

less heat

to

Methane Gas

Sources:

• _{Released by bacteria during decomposition of plants and}

animals

• _{Coal mining}

• _{Rice growing}

Methane Gas

Effects:

• _{Small amounts are harmless.}

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

the sun to produce a greenhouse effect which leads to global warming

Control

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}

Ozone

Source:

•

Sunlight acting on unburnt hydrocarbons and

nitrogen dioxide from car exhausts

Effect:

•

Causes

asthma attacks

and

eye irritation

Control:

Unburnt Hydrocarbons

Source:

•

Produced by car exhausts

Effect:

•

Known to produce ozones

Control:

•

Reduce vehicle emissions of pollutants using

catalytic

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

Air Pollution in Singapore

•

Singapore currently faces the issue of haze

•

Haze is caused by particles generated from:

–

Industrial activities

–

Burning of vegetation which is then carried by

winds across the region

• _{E.g. slash and burn method used to clear forests}

Air Pollution in Singapore

•

Haze has very detrimental effects. It causes:

–

Reduced visibility

–

Breathing problems such as bronchitis or asthma

–

Irritation of the eyes

•

Haze contains several pollutants which are

Haze

Haze

fine and dry particles that are suspended in air

INHALABLE PARTICLES fine and dry particles that are

suspended in air

ORGANIC COMPOUNDS

ORGANIC COMPOUNDS

Carbon monoxide (CO)

Nitrogen dioxide (NO₂)

Sulfur dioxide (SO₂)

Ozone (O₃)

Adapted from Ministry of Education (MOE)

Air Pollution in Singapore

•

Singapore monitors the haze situation by regularly

measuring the air quality

•

Air quality is measured by pollutant standard index

(PSI)

– _{This measures the amount of pollutants in the air}

– _{PSI levels can be obtained from the National Environment}

Air Pollution in Singapore

PSI Air Quality Descriptor Health Advisory

0 – 50 Good Normal Activities

51 – 100 Moderate

101 – 200 Unhealthy Reduce prolonged strenuous activities 201 – 300 Very unhealthy Avoid strenuous