2.9 - Atmospheric Pollution

What is a pollutant

A substance present in air that can cause harm to humans and the environment

Pollutants can be in the form of:

• Solid particles

• Liquid droplets

• Gases

Can pollutants be natural or man made?

Both

What is a greenhouse gas

A gas that absorbs heat in the atmosphere and prevents heat from escaping into space, keeping the Earth warmer

What type of greenhouse gas is CO2

Non-toxic

How is CO2 produced? (NATURALLY)

Natural processes:

• Volcanic eruptions

• Respiration of animals

• Burning or decay of organic matter

Why has the amount of CO2 in the air been increasing at an alarming rate since the Industrial Revolution?

Due to the burning of fossil fuels

What are the three fossil fuels?

• Coal

• Oil

• Natural Gas

What are fossil fuels primarily made of

Carbon and hydrogen

How do fossil fuels contribute to CO2 emissions?

They react completely with oxygen in air during combustion to produce CO2 and water vapour.

Represent this combustion reaction as a word equation

hydrocarbon + oxygen → carbon dioxide + water vapour

The industrial production of what else is a main contributor to the emission of CO2

Cement

Why does the concentration of CO2 in the atmosphere fluctuate between winter and summer

Because of seasonal variation in photosynthesis

How many extra million tonnes of CO2 are produced into the air because of the burning of fossil fuels

5000 million tonnes

What absorbs CO2 but is unfortunately being destroyed

Tropical rainforests

What can dissolve some of this extra CO2

oceans (not all CO2!!)

What happens to the rest of the CO2

It stays in the atmosphere, upsetting natures balance

What are other substances present in the atmosphere which are also greenhouse gases

• Water vapor

• Methane (CH4)

• CFCs

Why is the level of CH4 (methane) rising

Due to an increase in:

• Animal farming

• Rice farming

• Landfill sites

Without greenhouse gases, what would happen to our planet

It would be covered in ice with average temperatures 35C lower than at present

Does the temperature of earth have more to do with the greenhouse effect or our proximity to the sun

Greenhouse effect

Explain the greenhouse effect

1. Radiant energy from the sun are sent to earth as short infra-red waves. These warm the Earth.

2. The Earth then radiates this heat energy back into spaces as longer infrared waves.

3. However, greenhouse gases like carbon dioxide and water vapor in the air absorb some of this heat and send it back toward Earth.

4. This traps warmth, similar to how a greenhouse keeps plants warm.

Can infra-red radiated travel freely through the air surrounding the earth

No, unlike sunlight

What does an increase in greenhouse gases cause

A greater greenhouse effect → global warming

What do increasing global temperatures cause?

1. Polar ice-caps to melt and sea levels to rise

2. Low-lying areas of land to submerge under the sea

3. A change in climate and weather patterns all over the world. Extreme weather events (eg hurricanes and cyclones) would be more frequent.

4. Some agricultural areas will cease to produce crops and become deserts

5. Some species that cannot adapt with climate change (loss of natural habitat) will die out

What are tropical areas experiencing more of due to climate change

frequent and destructive storms and floods

To stop the increase in global temperature and stabilize atmospheric carbon dioxide concentration, how much do carbon dioxide emissions need to be reduced by

70-80%

How can this be done

• less consumption of fossil fuels

• Using renewable sources of energy

• Reduce reliance on cars

• More energy efficient buildings

• Improved power plant efficiency

• Planting more trees

• Kyoto protocol

• UN climate change conference

What is the Kyoto Protocol (1997)

The world’s primary international agreement on combating global warming. 100 counties committed to reduce their emissions of CO2 and 5 other greenhouse gases

What is the UN climate change conference

A discussion on the way forward on many issues including curbing CO3 production

What are the properties of carbon monoxide (CO)

• Colourless (gas)

• Odorless (gas)

• Non-irritating

• Very poisonous

What is carbon monoxide a product of?

Incomplete combustion of fuel - when a natural gas, coal or wood burns in a limited supply of air

Approx. how much CO is emitted into the atmosphere each year?

350 million tonnes

What is a major source of CO

Vehicular exhaust

Do all cars (petrol, diesel) produce CO

Yes

Do they check if car engines are producing CO at an acceptable level

Yes, in the VRT

What is another way CO is produced

From cigarette smoking

How does CO prevent the uptake of oxygen

It readily combined with haemoglobin in the red blood cells to form carboxyhaemoglobin

(doesn’t let oxygen bind with the haemoglobin → blood is not oxygenated→ oxygen is not carried around the body)

Does CO permanently bind with red blood cells

YES

Why do we say that CO “wastes blood”

Because it does not allow for the usual transfer of oxygen and carbon dioxide (gas exchange)

What does a shortage of oxygen make a person feel

• Headache

• Dizziness

• Sluggishness

What level of CO in the air causes death

0.1%

How is CO removed (vehicles) (3)

• Catalytic converters are fitted to the exhausts of many cars. The catalysts will oxidize carbon monoxide in the exhaust gases to CO2 (these convert CO to CO2 - not all though)

• New fuels may be used in the future - Some fuels (eg alcohol) burn more cleanly than hydrocarbons

• Vehicle engines can be tuned to take in more air and produce only CO2 and H2O - Unfortunately this increases the formation of NOx compounds (oxides of nitrogen)

What is a hydrocarbon

A hydrocarbon is a compound made up of only carbon (C) and hydrogen (H) atoms.

• Methane (CH4)

What is a combustion reaction

A chemical reaction in which a substance reacts rapidly with oxygen with the production of heat and light

What do the products of combustion of a hydrocarbon depend on

Whether the combustion reaction takes place in a:

• Plentiful supply of oxygen

• Limited supply of oxygen

What are all fossil fuels made up of

Hydrogen and Carbon

What are compounds made of H and C called

Hydrocarbons

Hydrocarbon examples

• Natural gas (methane)

• Petrol and diesel (crude oil)

• Wax

Diagram for determining what products are given as methane is burning

Process + Observations

Methane is it, air pump is switched on

• A colourless liquid condenses in the U-tube. This can be tested using anhydrous copper (II) sulphate which turns from white to blue (to test water was produced)

• Limewater turns milky (white precipitate) showing that carbon dioxide is produced

Word equation go summarize this

hydrocarbon + oxygen → water vapour + carbon dioxide

Chemical equation for when a methane buns in a plentiful supply of oxygen

What two products (ONLY) produced show that a hydrocarbon has undergone complete combustion

Carbon dioxide and water - ONLY!!

Fuels undergo ______ ______ when there is a plentiful supply of oxygen

Complete combustion

Fuels that burn with what flame give off the most heat energy possible

Blue flame

Why should you repeat this experiment without the fuel burning

Burning the fuel introduces more carbon dioxide and water vapor, which are already present in the air. Ensures accurate results

What difference will there be in the experiment

It will take much longer for the indicators to show a change

What is incomplete combustion

When a fuel does not burn in a sufficient amount of oxygen

What flame does it burn with in this case

A yellow same

What are the products of incomplete combustion

• Unburnt particulate carbon called soot (from flame)

• Carbon monoxide

• Water vapour

Chemical equation for incomplete combustion of methane

Compare between complete and incomplete combustion on these points:

Ok

Amount of oxygen available

Complete: plentiful supply of oxygen

Incomplete: limited supply of oxygen

Colour of flame

Complete: clean blue flame

Incomplete: yellow sooty flame

Products evolved

Complete: Carbon dioxide, water vapour

Incomplete: Carbon monoxide, water vapiur

Amount of energy released

Complete: Most heat energy released

Incomplete: Less heat energy released

Name the following properties of Carbon Dioxide and Carbon monoxide

Ok

Appearance

Carbon dioxide: colourless

Carbon monoxide: colourless

Odour

Carbon dioxide: Odourless

Carbon monoxide: Odourless

Effect on blue litmus

Carbon dioxide: turns damp blue litmus red (acidic oxide)

Carbon monoxide: no effect on litmus (neutral oxide)

Bubbling through lime water

Carbon dioxide: turns like water milky

Carbon monoxide: no reaction with like water

Bubbling through sodium hydroxide solution

Carbon dioxide: reacts with sodium hydroxide (neutralization reaction)

Carbon monoxide: no reaction

Reducing agent

Carbon dioxide: no

Carbon monoxide: yes

Combustion

Carbon dioxide: does not burn, used to extinguish fires

Carbon monoxide: burns with bright blue flame to give CO2

Toxicity

Carbon dioxide: Toxic at very high concentrations

Carbon monoxide: toxic at very low concentrations

What is the test used to distinguish between carbon dioxide and carbon monoxide

Bubbling them through calcium hydroxide (limewater)