Chemistry - Evolution of the Earth’s atmosphere

When did Earth form?

4.6 billion years ago

What was early Earth's atmosphere like?

Filled with water vapor, carbon dioxide, nitrogen, no oxygen as well as some gases like ammonia and methane.

Early Earth's atmosphere is similar to…

Mars and Venus's current atmosphere

How did the oceans form?

As the earth cooled, the water vapour in the air condensed to form the oceans

Why was the early Earth's atmosphere filled with these gases?

These gases were released by volcanic activity on early Earth

Why was early Earth so hot?

Lots of carbon dioxide in the atmosphere, trapping more heat as well as a large amount of volcanic activity on Earth's landmass

Why did nitrogen levels stay the same throughout the development of the atmosphere?

Nitrogen is an unreactive gas

What is the composition of Earth's modern atmosphere?

78% nitrogen, 21% oxygen, 0.9% (<1%) of argon and 0.04% of carbon dioxide

Why is evidence for Earth's early atmosphere limited?

It's difficult to gather evidence about the early atmosphere because it happened 4.6 billion years ago

How were landmasses created, on Earth?

As Earth cooled, its molten surface began to slowly solidify into landmasses

Why did carbon dioxide levels decrease?

As oceans formed, carbon dioxide dissolved into the oceans as the earth cooled

When did life first appear on Earth?

3.5 billion years ago where a photosynthetic bacteria grew

When did algae first start to produce oxygen on Earth?

About 2.7 billion years ago

What acid is produced when carbon dioxide dissolves in water?

carbonic acid

Why did oxygen levels increase in the atmosphere?

When algae formed in the oceans, algae, and other plants, began photosynthesising and releasing oxygen in the atmosphere while taking in carbon dioxide from the atmosphere

Word equation for photosynthesis

Carbon dioxide + water -> glucose + oxygen

How did sedimentary rocks first form in the oceans?

Animals fed on the photosynthesising plants which transferred carbon to their tissues including bones and shells and when these organisms died, their remains formed sedimentary rocks

How did fossil fuels first form?

Dead organisms, over a million years, turn into fossil fuels, such as crude oil, natural gas and coal which 'locked up' the carbon

Name one sedimentary rock

limestone

How did coal form?

Coal was formed from trees which were in dense forests in low-lying wetland areas. Flooding caused the wood from these forests to be buried in a way that prevented oxidation taking place. Compression and heating over millions of years turned the wood into coal.

how did crude oil and natural gas form in Earth's early atmosphere?

Crude oil and natural gas were formed from simple plants and tiny animals which were living in oceans and lakes. These small organisms died and their remains sank to the bottom where they were buried under sediments. The lack of oxygen prevented oxidation from occurring. Over millions of years, heat and pressure turned the remains of the organisms into crude oil and natural gas.

What are greenhouse gases?

Gases that trap heat in the atmosphere.

What are the 3 greenhouse gases?

carbon dioxide, methane, water vapor

What is the greenhouse effect?

The process by which gases hold heat in the atmosphere

How does the greenhouse effect work?

Short wavelength radiation (ultraviolet radiation) is emitted from the sun. When it strikes the earth's surface, some of it is absorbed and some is re-emitted from the surface of the Earth as long wavelength radiation (infrared radiation). Much of the radiation is trapped inside the Earth's atmosphere by greenhouse gases which can absorb and store the energy. Increasing levels of carbon dioxide and methane, although present in only small amounts, are causing significant upset to the Earth's natural conditions by trapping extra heat energy

Why is methane increasing in the atmosphere?

More waste being sent to landfill sites due to an increasing human population as well as increased levels of farming

Why are carbon dioxide levels increasing in the atmosphere

The increased demand for energy resulting in more fossil fuels being burned as well as deforestation as fewer trees means less carbon dioxide is removed from the atmosphere by photosynthesis

Why do many scientists agree that human activities have caused an increase in the temperature of the Earth's atmosphere at the surface?

Peer-reviewed evidence gives a clear correlation between the percentage of CO2 in the atmosphere and the changes in temperature

What should you consider when evaluating the quality of evidence of an issue like global warming?

Who did the research and whether they are trustworthy, skilled and experienced, who funded the research because that might cause some bias, what methods were used to collect and analyse the data because that might cause uncertainties in the evidence base and which organisation is reporting or publishing the evidence

Farming ____ and _ releases methane

Farming rice and cattle releases methane

What is complete combustion?

Where a fuel is burnt in a sufficient amount or in a good supply of oxygen which releases the maximum amount of energy

Word equation for complete combustion (of methane).

Methane + oxygen -> carbon dioxide + water

Symbol equation for complete combustion (of methane)

CH4 + 2O2 —-> CO2 + 2H2O

Why is climate science complicated?

As it is difficult to predict and explain what will happen to global temperatures in the future.

What is climate?

The average weather over large areas over a long period of time

What is weather?

The day-to-day condition of the atmosphere

What is global warming?

The rise in the average temperature of the Earth's surface.

Climate change

Long-term alteration of temperature and weather patterns around the world

Suggest two reasons why climate change leads to rising sea levels.

Water from melting glaciers and polar ice enters the oceans. Another reason is as the Earth's temperature increases, seawater warms up and expands.

The effects of global warming include:

Glaciers and polar ice melting, sea levels rising, patterns of rainfall changing producing floods or droughts as well as habitats changing

Effects of climate change:

Sea levels rising due to ice caps melting, increased severity and frequency of extreme weather like tropical storms, extreme drought, extreme heatwaves; causing wildfires and extreme rainfall; causing flooding

How is climate change causing more extreme and destructive weather?

Warmer ocean surfaces mean more moisture is entering the atmosphere so storms and hurricanes are more energetic and destructive

cause of global warming

Increased amounts of greenhouse gases present in the Earth's atmosphere.

Consequences of rising sea levels

This results in destructive erosion to coastal regions, flooding of wetlands and habitat destruction for birds, fish and plants, low lying cities are likely to see increased flooding and permanent loss of usable land without expensive barrier systems, increased soil salinity (salt concentration in soil) is also a consequence of rising sea levels

Consequences of extreme droughts

Some regions are seeing devastating droughts leading to crop failure and collapse of agricultural production which means that food production is greatly compromised leading to hardship and starvation

Consequences of extreme heatwaves

great loss of life and destruction of infrastructure and ecosystems

Consequences of extreme rainfall

Changing rainfall patterns are leading to uneven distribution of freshwater supplies, this causes a lack of reliable freshwater supplies resulting in economic and political instability as neighbouring countries compete for dwindling resources

What is carbon footprint

the total amount of carbon dioxide and other greenhouse gases emitted over the full life cycle of a product, service or event

What can be included in a carbon footprint of a car?

The machinery and processes of metal extraction used to manufacture the car as well as the power stations which generate electricity used to manufacture the car, the car itself when it's driven for many years and the machinery used to dispose of or recycle the car

What can be used to evaluate the carbon footprint of a person?

The carbon footprint of a person during one year would consist of the total amount of carbon dioxide released into the atmosphere by all of the activities they take part in, and the manufacture, use and disposal of all the products and resources they use

Give examples of activities that contribute to a carbon footprint

use electricity at home, probably generated from fossil fuels, for lighting their room and using electronic devices, using a gas-powered boiler at home (which produces carbon dioxide) for heating and hot water, travelling to school by bus or car (which probably runs on petrol or diesel), eating beef or rice which have been farmed using methods that release methane or travelling abroad once per year on an aeroplane (which produces carbon dioxide)

How can we reduce our carbon footprint?

Use more renewable energy sources e.g. solar power and wind turbines, reducing the amount of fossil fuels that are combusted by using less electricity and heating (energy) as well as recycling more natural materials e.g. metals and plastics as well as travelling less by unsustainable vehicles.

What is incomplete combustion?

When a fuel burns in insufficient oxygen, producing carbon monoxide as a toxic product, this method of combustion releases less energy

Fuel

a material that releases energy when it burns.

Fossil fuel

Coal, oil, natural gas, and other fuels that are ancient remains of plants and animals.

Particulate

a tiny particle of solid that is suspended in air or water

Carbon monoxide

a colorless, odourless, toxic and flammable gas formed by incomplete combustion of a fuel

What are two possible carbon products of incomplete combustion

Carbon Monoxide or Carbon Particulates (in the form of soot)

Coral Bleaching

A phenomenon in which algae inside corals die, causing the corals to turn white.

cause of coral bleaching

Prolonged exposure to high water temperatures and solar radiation

The word equation of incomplete combustion is

Fuel + Oxygen —-> Carbon Monoxide + Water

Symbol equation for incomplete combustion (use ethane as the fuel)

2C2H6 + 5O2 —-> 4CO + 6H2O

Problems of carbon monoxide

Carbon monoxide is a poisonous gas which binds to haemoglobin in your red blood cells, preventing them from carrying oxygen to the cells in your body. Carbon monoxide is colourless and has no smell, so it is very difficult to tell if you are breathing it in. It can be detected by electronic detectors which are often fitted near to boilers.

Problems with carbon particulates

Particulate carbon can cause health problems for humans because it irritates the lining of the lungs, can make asthma worse, and perhaps even cause cancer. Particulate carbon can also cause global dimming, which may reduce rainfall. It can also cover buildings and statues, making them look unclean.

What is global dimming?

Global dimming is the gradual reduction in radiation energy which reaches the Earth's surface from the Sun due to small particles in the atmosphere which have been produced by human activities like burning fossil fuels.

Consequences of global dimming

Can reduce rainfall as it can lower evaporation, reducing rainfall in certain areas, the decreased sunlight can also lead to lower crop yields impacting global food security and it can reduce the sky's visibility as it reduces sunlight to the Earth.

What can be used to assess a carbon footprint?

A life cycle assessment

What will the life cycle assessment consider in their measurements?

The extraction of a raw material, how a product is manufactured and distributed and finally how the product is disposed at the end of its life

How are businesses reducing their carbon footprint?

Governments and global organisations are encouraging businesses to switch to more renewable and sustainable energy sources by implementing higher taxes if the business is releasing a large amount of greenhouse gases and waste into the environment.

Carbon capture

Carbon capture refers to a range of technologies used to trap atmospheric carbon dioxide from power generation and other industries, the carbon dioxide is stored deep underground in porous rocks from which oil and gas have been extracted

source of carbon dioxide (CO2)

Complete combustion of any fuel containing carbon atoms as well as deforestation

Source of carbon monoxide and carbon particulates (soot)

Incomplete combustion of any fuel containing carbon atoms

Source of unburned hydrocarbons

Hydrocarbon fuel molecules which have not been oxidised at all

Source of sulphur dioxide (SO2)

Combustion of a fossil fuel which contains sulfur impurities, as the sulphur also becomes oxidised to form a gas

Source of nitrogen oxides (NOx)

Oxidation of atmospheric nitrogen inside the engine of a vehicle like a car or lorry

What are the 3 nitrogen oxides (NOx)

Nitric Oxide (NO), Nitrogen Dioxide (NO2), Nitrous Oxide (N2O)

Cause of sulphur dioxide

Sulfur dioxide is caused when sulfur atoms which are present in some fossil fuels are oxidised

Oxidation of sulphur (word equation)

Sulphur + Oxygen —-> Sulphur Dioxide

Oxidation of sulphur (symbol equation)

S + O2 —-> SO2

Oxidation of sulphur dioxide (word and symbol)

Word: Sulfur Dioxide + Oxygen —-> Sulfur Trioxide, Symbol: 2SO2 + O2. —> 2SO3

Acid rain

A dilute (weak) solution of sulphuric acid (H2SO4)

Acid rain is caused by

Rain that contains dissolved acidic gases such as nitrogen oxides and sulphur trioxide

The word and symbol equation for the creation of acid rain

Sulfur Trioxide + Water —-> Sulfuric Acid, SO3 + H2O —-> H2SO4

Effects of acid rain

Acid rain harms and kills plants and animals, especially those that live in aquatic environments. It can also damage man-made objects like statues and buildings. It also pollutes crop and water supplies and irritates lungs, throat and eyes.

How are nitrogen oxide pollutants formed?

Nitrogen is not present in fuels, but the high temperatures and pressures inside a car engine can cause the nitrogen and oxygen in the air to react together to make oxides of nitrogen.

The word and symbol equation for the creation of acid rain by nitrogen oxides

Nitrogen Dioxide + Water —-> Nitric Acid + Nitrous Acid, 2NO2 + H2O —-> HNO2 + HNO3

What types of acid are nitrous acid (HNO2) and nitric acid (HNO3)?

Nitrous acid is a weak acid while nitric acid is strong acid

What else can nitrogen oxide pollutants cause, apart from acid rain

Photochemical smog

What is photochemical smog?

A type of air pollution that appears as a visible smoky fog which is very harmful to health.

Effects of smog

Smog can have major health effects, causing asthma attacks and even death

Diesel sometimes contains sulfur impurities. List the pollutants which could be produced when it is burned incompletely inside a car engine.

Carbon monoxide, particulate carbon, sulfur dioxide and nitrogen oxides.

What is the name of the atmospheric process which keeps the Earth warm by absorbing radiation from the Sun?

greenhouse effect

Which is a cause of global warming?

Burning fossil fuels to generate electricity

What do the vast majority of scientists believe about global warming?

It is caused by human activities

What is an effect of global warming? (Extreme Rainfall)

Flooding of low lying coastal land

What can help to reduce the effects of global warming? (Extreme Drought)

Planting drought-resistant crop

Oxidation of nitrogen (word and symbol)

Nitrogen + Oxygen —-> Nitric Oxide, N2 + O2 —> 2NO

Oxidation of Nitric Oxide (word and symbol)

2NO + O2 —-> 2NO2

How does waste contribute to a large carbon footprint?

Because decomposers need to break it down and this produces methane

How does air pollution spread from one place to another?

Through the wind or through natural processes like diffusion