C9

Question 1

For 200 million years, proportions of gases in the atomosphere have been the same as today, state the percentage of each gas in the atmosphere

Answer 1

• about four-fifths (approximately 80%) nitrogen
• about one-fifth (approximately 20%) oxygen
• small proportions of various other gases, including carbon dioxide, water vapour and noble gases.

Question 2

What has happened with theories of what Earth was like in the early atmosphere and why?

Answer 2

Theories about what was in the Earth’s early atmosphere and how the atmosphere was formed have changed and developed over time. Evidence for the early atmosphere is limited because of the time scale of 4.6 billion years.

Question 3

What does one theory suggest about the first billion years of the Earth’s existence?

Answer 3

One theory suggests that during the first billion years of the Earth’s existence there was intense volcanic activity that released gases that formed the early atmosphere and water vapour that condensed to form the oceans. At the start of this period the Earth’s atmosphere may have been like the atmospheres of Mars and Venus today, consisting of mainly carbon dioxide with little or no oxygen gas.

Volcanoes also produced nitrogen which gradually built up in the atmosphere and there may have been small proportions of methane and ammonia.

When the oceans formed carbon dioxide dissolved in the water and carbonates were precipitated producing sediments, reducing the amount of carbon dioxide in the atmosphere. No knowledge of other theories is required.

Question 4

Note:

Answer 4

AQA says that students should be able to, given appropriate information, interpret evidence and evaluate different theories about the Earth’s early atmosphere.

Question 5

How did oxygen get into the atmosphere?

Answer 5

Algae and plants produced the oxygen that is now in the atmosphere by photosynthesis

Question 6

What is the symbol equation for algae and plants producing oxygen?

Answer 6

6CO2 + 6H2O ——> C6H12O6 + 6O2

Question 7

What is the word equation for algae and plants producing oxygen?

Answer 7

Light
carbon dioxide + water ———-> glucose + oxygen

Question 8

When did algae first produce oxygen and what happened after?

Answer 8

Algae first produced oxygen about 2.7 billion years ago and soon after this oxygen appeared in the atmosphere. Over the next billion years plants evolved and the percentage of oxygen gradually increased to a level that enabled animals to evolve.

Question 9

What did algae and plants decrease the percentage of?

Answer 9

Algae and plants decreased the percentage of carbon dioxide in the atmosphere by photosynthesis.

Question 10

What was another way carbon dioxide was reduced?

Answer 10

Carbon dioxide was also decreased by the formation of sedimentary rocks and fossil fuels that contain carbon.

Question 11

What are the main changes in the atmosphere over time and some of the likely causes of these changes?

Answer 11

Intense volcanic activity – water vapour, carbon dioxide, nitrogen, ammonia, methane released. Water vapour condensed to form oceans. Atmosphere mostly carbon dioxide; nitrogen slowly building up over time.

Question 12

Describe and explain the formation of deposits of limestone, coal, crude oil and natural gas.

Answer 12

When the plants, plankton and animals died, they fell to the bottom of the seabed and got buried by layers of sediment (mud). Over millions of years, heat and pressure turned the dead material into fossil fuels (coal, crude oil and natural gas) or limestone.

Question 13

What do greenhouse gases in the atmosphere maintain and state examples of greenhouse gases

Answer 13

Greenhouse gases in the atmosphere maintain temperatures on Earth high enough to support life.

Water vapour, carbon dioxide and methane are greenhouse gases.

Question 14

Describe the greenhouse effect in terms of the interaction of short and long wavelength radiation with matter

Answer 14

Electromagnetic radiation from the Sun passes through the Earth’s atmosphere.
The Earth absorbs electromagnetic radiation with short wavelengths.
Heat is radiated from the Earth as longer wavelength infrared radiation.
Some of this infrared radiation is absorbed by greenhouse gases in the atmosphere.
The atmosphere warms up

Question 15

Some human activities increase the amounts of greenhouse gases in the atmosphere. What do they include?

Answer 15

• carbon dioxide
• methane.

Question 16

Statw two human activities that increase the amounts of each of the greenhouse gases carbon dioxide and methane

Answer 16

burning fossil fuels in industry, vehicles and power stations releases carbon dioxide.

farming cattle and growing rice in paddy fields releases methane.

Question 17

Based on peer-reviewed evidence, what do scientists believe that human activities will cause the temperature?

Answer 17

It will cause the temperature of the Earth’s atmosphere to increase at the surface and that this will result in global climate change.

Question 18

What is a drawback to global climate change?

Answer 18

However, it is difficult to model such complex systems as global climate change. This leads to simplified models, speculation and opinions presented in the media that may be based on only parts of the evidence and which may be biased.

Question 19

Note:

Answer 19

AQA says that students should be able to:

• evaluate the quality of evidence in a report about global climate change given appropriate information
• describe uncertainties in the evidence base
• recognise the importance of peer review of results and of communicating results to a wide range of audiences.

Question 20

What is a major cause of climate change?

Answer 20

An increase in average global temperature

Question 21

Describe briefly four potential effects of global climate change

Answer 21

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

Question 22

Discuss the scale, risk and environmental implications of global climate change

Answer 22

extreme weather events. severe impacts on the world’s poorest and most vulnerable populations. environmental and economic damage. large-scale singular events (such as further sea level rise as major ice sheets melt over Greenland and Antarctica)

Question 23

What is the carbon footprint?

Answer 23

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

Question 24

How can the carbon footprint be reduced?

Answer 24

The carbon footprint can be reduced by reducing emissions of carbon dioxide and methane.

Question 25

Describe actions to reduce emissions of carbon dioxide and methane

Answer 25

Encourage composting or incineration (reduces the amount of biodegradable material going to landfill). Capture the methane produced and use it as fuel or to generate electricity when burnt. Reduce the number of farm animals (for example, by encouraging people to eat less meat).

Question 26

Why may actions to reduce emissions of carbon dioxide and methane be limited?

Answer 26

Firstly, lower than expected demand for a commodity results in lower prices making a further reduction in demand more difficult. Coal is a clear example. Coal producers have for a long time overestimated demand resulting in a decade of overinvestment.

Question 27

What is a major source of atmospheric pollutants?

Answer 27

The combustion of fuels

Question 28

What do most fuels contain (including coal) ?

Answer 28

Carbon,hydrogen and some sulfur

Question 29

What a gas is released into the atmosphere when a fuel is burned, what does it include?

Answer 29

The gases released into the atmosphere when a fuel is burned may include carbon dioxide, water vapour, carbon monoxide, sulfur dioxide and oxides of nitrogen. Solid particles and unburned hydrocarbons may also be released that form particulates in the atmosphere.

Question 30

Describe how carbon monoxide, soot (carbon particles), sulfur dioxide and oxides of nitrogen are produced by burning fuels

Answer 30

When fuels burn completely the gases released into the atmosphere include carbon dioxide, water (vapour), and oxides of nitrogen. Sulfur dioxide is also released if the fuel contains sulfur. When fuels burn in a limited supply of air carbon monoxide is produced. Solid particles (soot) may also be produced

Question 31

Note:

Answer 31

AQA wants students to be able to predict the products of combustion of a fuel given appropriate information about the composition of the fuel and the conditions in which it is used.

Question 32

What is carbon monoxide?

Answer 32

Carbon monoxide is a toxic gas. It is colourless and odourless and so is not easily detected.

Question 33

What does sulfur dioxide and oxides of nitrogen cause?

Answer 33

Respiratory problems in humans and cause acid rain.

Question 34

What do particulates cause?

Answer 34

Particulates cause global dimming and health problems for humans.

Question 35

Describe and explain the problems caused by increased amounts of these pollutants in the air

Answer 35

AAAAA