C.11

Question 1

What gases make up the atmosphere today?

Answer 1

• 78% - Nitrogen
• 21% - Oxygen
• Rest - other gases such as carbon dioxide, methane, water vapour

Question 2

What was the atmosphere like millions of years ago?

Answer 2

There was a far greater amount of carbon dioxide, and a very little amount of nitrogen and oxygen.

Question 3

Why are scientists uncertain regarding the Earth’s early atmospheric state?

Answer 3

As the Earth is around 4600 million years old, and it is difficult to track the atmosphere that far back in time.

Question 4

How do scientists believe the atmosphere was formed?

Answer 4

It is widely believed that volcanic activity released the gases that make up the atmosphere, including water vapour which condensed to form the oceans.

Question 5

Why has the concentration of oxygen in the atmosphere increased?

Answer 5

Oxygen levels have increased as a result of photosynthesis by early photosynthetic plants and algae.

Question 6

Why did the levels of CO2 greatly decrease?

Answer 6

A lot of CO2 dissolved into the oceans as a weak acid, eventually forming minerals, corals and carbonate rock.

Some CO2 has been absorbed by photosynthetic plants, used to produce oxygen and trapped in fossil fuels.

Question 7

How does coal form?

Answer 7

Coal forms from the remains of trees and ferns which have not decomposed due to a lack of oxygen or acidic conditions. These remains were covered by sediment and compressed, where the pressure and high temperatures formed coal.

Question 8

How does oil and natural gas form?

Answer 8

They are formed by dead plankton which hasn’t decomposed on the seabed. The plankton gets compressed by sediment where heat and pressure converts it into crude oil and natural gas.

• Remember that natural gas usually consists of methane which is a hydrocarbon (link to crude oil)

Question 9

What are three of the main greenhouse gases?

Answer 9

• Carbon Dioxide
• Water vapour
• Methane

Question 10

How is the greenhouse effect caused?

Answer 10

Energy from the sun (such as UV and visible light) travels to the Earth as short wavelength radiation. Most of it passes through the atmosphere easily as short wavelength radiation does not interact strongly with the gases in the atmosphere.

The radiation is absorbed by the Earth and energy is reflected back into space as long wavelength radiation. A lot of this energy gets trapped in the atmosphere as it DOES interact with the gases. As a result, temperature increases.

Question 11

Why is the greenhouse effect important?

Answer 11

It is necessary as it helps keep the Earth warm enough to sustain life.

Question 12

How are atmospheric levels of CO2 increasing?

Answer 12

Burning fossil fuels and deforestation

Question 13

How are the atmospheric levels of Methane increasing?

Answer 13

Through agriculture such as rice farming and cattle farming.

Question 14

What are 4 effects of climate change?

Answer 14

• Land ice melting - increases sea levels and can lead to floods
• More frequent extreme weather events
• Animal distribution changes
• Can change the distribution of protist diseases

Question 15

Why is it difficult to predict future climate change?

Answer 15

The future of climate change depends on human activity, such as the use of renewables, changes in population and the use of new technologies.

Question 16

What is meant by carbon footprint?

Answer 16

The total amount of greenhouse gases emitted of the full life cycle of a product, service or event

Question 17

How can CO2 emissions be reduced?

Answer 17

• Insulating homes and not using the heating
• Not driving cars and using public transport
• Using renewable energy resources
• Using energy saving appliances

Question 18

How can methane emissions be reduced?

Answer 18

• Consuming less cattle produce (beef and dairy)
• Trapping and burning methane in landfill to use for producing electricity

Question 19

Why is it difficult to reduce greenhouse gas emissions?

Answer 19

It can be expensive, inconvinient and people are often unlikely to adapt to changes

Question 20

What is the definition of a fuel?

Answer 20

A fuel is something which releases energy when combusted

Question 21

What are the products of complete combustion and why?

Answer 21

Carbon dioxide and water. These are produced as most fuels contain carbon and hydrogen which become oxidised when reacted with oxygen.

Question 22

Why is incomplete combustion caused and why is it a problem?

Answer 22

A lack of oxygen in combustion is dangerous as it produces carbon monoxide, a toxic, odourless and colourless gas. Carbon monoxide can be detected using a carbon monoxide detector.

Question 23

What are three dangerous products of combustion?

Answer 23

• Sulfur dioxide
• Oxides of nitrogen
• Particulates

Question 24

How does sulfur dioxide and nitrous oxides (NOx) form?

Answer 24

Coal contains sulfur which reacts with oxygen when combusted, forming sulfur dioxide.

Nitrous oxides are produced in engines such as by cars, as high temperatures cause nitrogen and oxygen to react.

Question 25

What are the dangers of nitrous oxides and sulfur dioxide?

Answer 25

They both cause breathing problems and disolve in rainwater to form acid rain which damages trees and corrodes limestone buildings.

Question 26

What are particulates and why are they dangerous?

Answer 26

Particulates are particles of carbon (soot) and unburned hydrocarbons.

They are dangerous as they increase the risk of heart and lung diseases and they lead to global dimming as they block out energy and light from the sun. This has been shown to affect rainfall patterns.