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Chemistry > topic 9 - chemistry of the atmosphere > Flashcards

topic 9 - chemistry of the atmosphere Flashcards

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1
Q

Name the gases in the atmosphere today and state the proportions of each gas

A
  • Around 78% of nitrogen
  • Around 21% is oxygen
  • There are also small proportions of other gases (e.g carbon dioxide water vapour and noble gases such as argon)
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2
Q

Describe the Earth’s early atmosphere

A
  • The early atmosphere consisted mainly of carbon dioxide with small but increasing amounts of nitrogen
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3
Q

Describe the theory on how the Earth’s atmosphere was formed

A
  • 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.
  • 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 and reducing the amount of carbon dioxide in the atmosphere.
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4
Q

Why is evidence for the early atmosphere limited?

A

because of the time scale of 4.6 billion years

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5
Q

How did the amount of oxygen in the atmosphere increase?

A
  • algae and plants produced the atmospheric O2 by photosynthesis, which can be represented by the equation:

6 CO2 + 6 H2O + light –> C6H12O6 + 6 O2
- As the amount of O2 gradually increased, there were more plants that produced more oxygen and the percentage of oxygen gradually increased to a level that enabled animals to evolve

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6
Q

How did the amount of carbon dioxide in the atmosphere decrease?

A
  • Algae and plants decreased the percentage of carbon dioxide in the atmosphere through photosynthesis
  • Carbon dioxide was also decreased by the formation of sedimentary rocks and fossil fuels that contain carbon
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7
Q

How is coal formed?

A
  • coal is formed from the remains of ferns and trees
  • if they die in marshy wetlands then they do not decompose
  • this can be due to the lack of oxygen and acidic conditions
  • these both prevent bacteria from carrying out decomposition
  • Over time, the plant remains are covered with sediment and compressed
  • High temperature and pressure creates coal
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8
Q

How is crude oil formed?

A
  • crude oil is formed from plankton, which are tiny plants and animals found in the sea
  • when these die, they settle in mud on the sea-bed
  • if oxygen is not present then they do not decompose
  • Over time, they are compressed by sediment
  • Heat and pressure convert them into crude oil
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9
Q

How is natural gas formed?

A
  • Natural gas is formed from plankton, in a similar way to crude oil
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10
Q

State the main greenhouse gases

A
  • water vapour, carbon dioxide and methane
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11
Q

What is the function of greenhouse gases?

A

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

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12
Q

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

A
  • The greenhouse effect allows short wavelength radiation from the sun to pass through the atmosphere to the Earth’s surface but absorbs the outgoing long wavelength radiation from the Earth causing an increase in temperature
  • Without the greenhouse effect, the Earth would be too cold for most living organisms to survive
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13
Q

How have human activities led to an increase in carbon dioxide?

A

combustion - we burn coal for electricity, petrol and diesel to power cars and gas to heat our homes
deforestation - in many cases, the forests are simply burned to provide land for grazing cattle. Burning forests release large amounts of carbon dioxide

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14
Q

How have human activities led to an increase in methane?

A
  • methane is released in agriculture e.g. growing rice in flooded paddy fields
  • methane is also released when cattle such as cows pass wind
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15
Q

What is the effect of an increase in greenhouse gases?

A
  • This causes the temperature of the atmosphere to rise as more of the energy from the sun is trapped
  • Rising temperatures will increase the melting of the polar ice sheets and glaciers
  • This will lead to increased sea levels
  • Increased sea levels could lead to more flooding of low-lying areas
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16
Q

What are the effects of global climate change?

A
  • climate change could lead to more severe weather e.g. more storms in the UK
  • increasing temperatures could change the distribution of animals such as insects
  • it may even change the distribution of insect-borne diseases such as malaria
17
Q

Describe the process of peer review

A
  • Many scientists believe that climate change is caused by human activity causing the release of greenhouse gases
  • That is because the evidence for climate change is shared between many different scientists
  • These scientists can then criticise the evidence and decide whether it is valid
18
Q

what is the benefit of peer review?

A
  • allows scientists to detect false claims e.g. based on poor evidence, biased
19
Q

Describe how models of climate change are not always accepted by everyone

A
  • climate change is complex and difficult to model
  • stories about climate change in the media can be simplified or simply biased
  • scientists must work harder to communicate their ideas around climate change to the general public
  • we cannot predict with certainty how much the temperature of the atmosphere will increase -> this can lead to speculation in the media
20
Q

What is a carbon footprint?

A

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
- the carbon footprint can be reduced by reducing emissions of carbon dioxide and methane

21
Q

How can we reduce carbon dioxide emissions?

A
  • a lot of energy is used to heat our homes. This often comes from burning fossil fuels
    -> By insulating our homes or turning down the heating, we can reduce carbon dioxide emissions
  • a great deal of carbon dioxide is released by driving cars
    -> we can reduce this by using public transport such as buses and trains. This releases less carbon dioxide per passenger
  • a lot of carbon dioxide is produced by generating electricity by burning fossil fuels
    -> we can reduce that by switching to renewable sources of electricity e.g. wind power
    -> on a personal level, we can reduce the amount of electricity we use at home, by switching to energy-saving lightbulbs, and turning appliances off at the plug rather than leaving them on standby
22
Q

What are the problems with reducing the carbon footprint?

A
  • Most of these solutions are expensive and people are reluctant to pay
    -in some cases they are inconvenient - many people prefer the convenience of driving over public transport
23
Q

How can we reduce methane emissions?

A
  • One of the sources of methane is agriculture
    -> one way to reduce that is for people to eat less beef and fewer dairy products
  • Another source of methane is landfills
    -> we can reduce this by trapping the methane and burning it to produce electricity. That is a good idea because methane is a much more powerful greenhouse gas than carbon dioxide
24
Q

What are the problems with reducing methane emissions?

A
  • people who enjoy eating beef and dairy products are unlikely to change their diets
  • trapping and burning methane costs money
25
Q

What are fuels?

A

Fuels are substances which release energy when they are combusted

26
Q

What do most fuels contain?

A

Carbon and hydrogen

27
Q

What happens when fuels containing carbon and hydrogen are burnt?

A
  • when burning fuels such as these, the carbon and hydrogen atoms react with oxygen in the air
  • in other words, these elements are oxidised
28
Q

What is complete combustion?

A

methane + oxygen -> carbon dioxide + water
- the carbon atom in the methane molecule has been oxidised to form the gas carbon dioxide
- the hydrogen atoms have been oxidised to form water vapour

29
Q

What happens if the amount of oxygen is reduced during combustion?

A
  • carbon monoxide replaces carbon dioxide
30
Q

What is carbon monoxide?

A
  • Carbon monoxide is a toxic gas and it has no colour and no smell
31
Q

How is sulfur dioxide produced?

A
  • Some fuels such as coal contain the element sulfur
  • When coal is burned, the sulfur atoms are oxidised (react with oxygen)
  • This produces the gas sulfur dioxide

S + O2 -> SO2

32
Q

How are oxides of nitrogen produced?

A
  • Here, high temperatures cause nitrogen and oxygen from the air to react
  • This produces a range of different molecules so scientists call them oxides of nitrogen
33
Q

What are the effects of sulfur dioxide and oxides of nitrogen?

A
  • Both can cause breathing problems in humans
  • They also dissolve in rainwater to form acid rain
34
Q

What is the effect of acid rain?

A
  • Acid rain can damage trees and corrode buildings made from limestone
35
Q

What are particulates?

A
  • particles of carbon (soot) and unburned hydrocarbons
36
Q

What are the effects of particulates?

A
  • Particulates can damage human health e.g. they increase the risk of heart disease and lung disease
  • they can also reduce the amount of energy from the sun that reaches the earth’s surface
  • Scientists call this global dimming, it is possible global dimming is affecting rainfall patterns

Chemistry (10 decks)

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