Chemistry : C9

What was phase 1 of the evolution of the atmosphere?

For the first billion years, the Earth’s surface was covered in volcanoes that erupted and released lots of gases.

Mostly carbon dioxide with extremely little oxygen.

Volcanic activity released nitrogen, water vapour and small amounts of methane and ammonia.

What was phase 2 of the evolution of the atmosphere?

Water vapour in the atmosphere condensed to form oceans.

Carbon dioxide was removed from the atmosphere as it was dissolved by the oceans to form carbonate precipitates under the seabed.

Green plants and algae evolved and absorbed carbon dioxide, beginning to carry out photosynthesis. Marine animals later evolved.

Some of the carbon these organisms took in became fossil fuels and rocks over time.

What was phase 3 of the evolution of the atmosphere?

Green plants and algae produced oxygen by photosynthesis.

Algae evolved first and then green plants did too.

As oxygen levels built up in the atmosphere more complex organisms like animals began to evolve.

Eventually, the atmosphere had reached a composition of what it is today. Carbon dioxide = 80% Oxygen = 20% Other gases = Less than 1%.

This happened around 200 million years ago.

How do algae and green plants create fossil fuels?

When plants, plankton and other marine animals die, they fall to the seabed and become buried by sediment.

They become compressed over years forming sedimentary rocks, oil and gas - carbon is trapped within them.

Crude oil and natural gas are formed by reserviours under the seabed when they get trapped in rocks.

Coal is a sedimentary rock made from thick plant deposits.

Limestone is a sedimentary rock made of carbon carbonate deposits.

Define carbon footprint

A measure of the amount of carbon dioxide and other greenhouse gases released over the full life cycle of something.

What are the 5 ways to reduce carbon footprint?

1. Using renewable energy sourced or nuclear energy instead of fossil fuels

2. Using efficient processes that conserve energy and cut out waste.

3. Governments can tax companies and individuals based on the amount of greenhouse gases they use.

4. Governments could put a cap on emissions of all greenhouse gases for companies

5. Using technology to measure the CO2 produced by burning fossil fuels before it’s released

Why is reducing carbon footprint hard?

1. A lot of work needs to be done on alternative technologies

2. Governments are worried these changes could impact economic growth

3. It’s hard to make international agreements to reduce emissions as each country has different opinions

4. Individuals in developed countries need to make change which some are reluctant to do

How do greenhouse gases impact the Earth’s temperature?

Greenhouse gases such as carbon dioxide, methane and water vapour act as an insulating layer in the Earths atmosphere.

This allows Earth to be warm enough to support life.

Particles are absorbed, greenhouse gases absorb long wavelength radiation that gets reflected back off the Earth.

It is then re-radiated in all directions such as back to the Earth, this thermal radiation warms up the Earth’s surface.

This is the greenhouse effect.

What forms of human activity impact the greenhouse effect?

1. Deforestation

2. Burning fossil fuels

3. Agriculture

4. Creating waste

What are the consequences of global warming?

1. Ice caps melting and rising sea levels, increased flooding and coastal erosion

2. Changes in rainfall patterns

3. Frequency and severity of storms increases

4. Changes in temperature and amount of water available

How does combustion increase air pollution?

Fossil fuels contain hydrocarbons.

During combustion the carbon and hydrogen in these compounds are oxidised so carbon dioxide and water vapour are released into the atmosphere.

Complete combustion occurs when there’s enough oxygen.

If there’s not enough oxygen, incomplete combustion takes place and unburnt fuel is released and carbon monoxide can be produced alongside carbon dixoide.

Particulates are released into the air.

What are the risks when particulates are released into the air?

If inhaled, they can get stuck in the lungs and cause damage leading to respiratory problems.

They are bad for the environment as they reflect sunlight back into space so less light reaches Earth, causing global dimming.

What are the risks of carbon monoxide?

It can stop your blood from carrying oxygen around the body.

It does this by binding to the haemoglobin in the blood that normally carries oxygen so less oxygen can be transported.

À lack of oxygen in the blood can lead to fainting, a coma or even death.

It is odourless and colourless making it hard to detec.

What else is released during combustion of fossil fuels?

What are the risks?

Sulfuro dioxide is released.

Nitrogen oxides are created from a reaction between nitrogen and oxygen in air caused by heat of burning.

The gases mix and form clouds of dilute sulfuric acid or dilute nitric acid.

This then falls as acid rain. Acid rain kills plants and damages buildings and statues, making metal corrode.

Can also cause respiratory problems if breathed in