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GCSE Chemistry > Chemistry of the atmosphere > Flashcards

Chemistry of the atmosphere Flashcards

1
Q

State the proportions of the gases in our Earth’s atmosphere:

A

For 200 million years, the proportions of different gases in the atmosphere have been much the same as they are today:

  • 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.
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2
Q

Describe the composition of the Earth’s atmosphere:

A
  • During the first billion years there was intense volcanic activity.
  • These volcanoes released gases such as water vapour and CO2 that formed the atmosphere.
  • As the Earth cooled water vapour condensed to form oceans
  • So at this point the Earth’s atmosphere mainly consisted of CO2 and H2O with little/no O2 (very similar to the atmosphere of Mars and Venus today).
  • Volcanoes also released small proportions of other gases such as nitrogen which gradually built up in the atmosphere (and methane and ammonia)
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3
Q

Difference between early atmosphere and today’s atmosphere.

A

Early atmosphere had a greater amount of CO2 but today’s atmosphere has lower amount

DUE TO:

  • More plants so more photosynthesis.
  • And as oceans formed CO2 dissolved into the water and carbonates were precipitated to produce sediments which reduced the amount of CO2 in early atmosphere.

The Early atmosphere contained very little oxygen, our atmosphere today has more oxygen.

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4
Q

How did CO2 in atmosphere decrease?

A
  • Dissolved in oceans
  • Dissolved in oceans to form a weak acid which reacted with minerals in the sea to form PRECIPITATES.
  • CO2 was decreased in atmosphere bc when it dissolved into water it was used to form SEDIMENTARY ROCK which contain carbon.
  • As more life evolved on earth = more plants (and algae) = more PHOTOSYNTHESIS so CO2 was used up.
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5
Q

How did O2 in our atmosphere increase?

A

Algae and plants produced O2 in our atmosphere from photosynthesis.

6CO2 + 6H20 -> C6H12O6 + 6O2

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

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6
Q

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

A

COAL
- Formed from the remains of ferns and trees.
- When these die in marshy wetlands they do not decompose (due to lack of oxygen or acidic conditions which prevent bacteria carrying out decomposition).
- Plant remains are covered with sediments and are compressed
- High temperature and pressure converts this to coal.

CRUDE OIL
- Formed from the remains of plankton
- When they die they settle at the bottom of the sea bed and do not decompose (due to lack of oxygen or acidic conditions which prevent bacteria carrying out decomposition).
- And over time they are compressed by sediments.
- High temp and pressure converts this to crude oil.

NATURAL GAS = mainly the HC methane
- Found typically near deposits of (crude) oil as they are both made in the same way ie
- Plankton dies and falls to bottom of sea bed.
- Doesn’t decay due to unfavourable conditions (lack of O2 and acidic conditions so bacteria can’t survive to carry out decomposition)
- Over time compressed
- High temp and pressure converts this to natural gas such as methane.

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7
Q

How were deposits of limestone formed?

A
  • CO2 dissolved in oceans formed by condensed water vapour.
  • This reacts with calcium hydroxide in oceans to form white calcium carbonate known as limestone.

(which is insoluble and so turns the limewater ‘milky’)

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8
Q

True or false, fossil fuels are non-renewable?

What is meant by a fossil fuel?

A

True.

Fossil fuels are a finite and non-renewable resource as they are formed over millions of years, that can be burnt to release energy.

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9
Q

True or false, all fossil fuels contain carbon?

A

True - carbon comes from carbon dioxide taken in by photosynthesis in plants.

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10
Q

What is meant by the greenhouse effect (in terms of shortwave and long-wave radiation).

A
  • Energy from Sun travels to the Earth as Short wavelength radiation.
  • Some short wavelength radiation is reflected back into space, but most passes back into the atmosphere.
  • Because short wavelength radiation does not interact strongly with gas molecules in the atmosphere, so is not absorbed by them.
  • Energy from short wavelength radiation is absorbed when it reaches the surface of the Earth.
  • The surface of the Earth radiates this energy as long wavelength radiation.
  • Some of the long wavelength radiation interacts with gas molecules of the greenhouse gases in the atmosphere, and is absorbed by them.
  • So because energy is trapped by atmosphere, this causes the energy in the atmosphere to increase.
  • This is important as it keeps the temperature on Earth warm enough to support life.
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11
Q

Formula for calcium carbonate.

A

CaCO3

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12
Q

What is the role of greenhouse gases?

A

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

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13
Q

Greenhouse gases, name them:

A
  • CO2
  • H2O vapour
  • Methane
  • Nitrogen
  • Ammonia
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14
Q

Two human activities that increase the levels of CO2 in our atmosphere:

A
  • Burning fossil fuels
  • Deforestation (less CO2 absorbed for photosynthesis)
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15
Q

Two human activities that increase the levels of methane in our atmosphere:

A
  • Rearing cattle such as cows; when they pass wind
  • Decay of organic waste in landfill sites.
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16
Q

Describe 4 potential effects of global climate change.

A
  • Melting glaciers (due to rising temp) leading to increased sea levels and more flooding of low-lying areas.
  • Extinction of species.
  • Extreme weather
  • Decrease in crop yield.
17
Q

How have scientists concluded that climate change is caused by human activity releasing greenhouse gases?

A
  • Because the evidence for climate change is shared between many scientists.
  • Scientists criticise evidence and determine if it is valid.
  • This is known as peer-review.
18
Q

What is meant by peer-review?

A

When evidence is shared between many scientists and scientists criticise evidence and determine if it is valid.

19
Q

Why is peer-review important?

A

It allows scientists to detect false claims, eg those based on poor evidence/bias.

20
Q

Why is there a problem with our understanding of climate change?

A
  • Climate change is complex and difficult to model.
  • So we may see simplified or biased stories about climate change in the media, or speculation based on only part of evidence

^^This is why scientists work harder to communicate ideas about climate change to the general public.

21
Q

What are some uncertainties surrounding climate change?

A

We cannot predict with certainty how much the temperature of the climate will increase leading to further speculation in the media.

22
Q

What is meant by carbon footprint?

A

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

23
Q

How can carbon footprint be reduced?

A

By reducing emissions of carbon dioxide and methane.

CO2
- Take public transport (less CO2 per passenger)
- Reduce the combustion of fossil fuels;
1- insulate homes to use less heating; 2 - use renewable sources of electricity eg wind power

ISSUE;
expensive

METHANE (CH4)
- Grazing cattle causes methane to be released when the pass wind
- Landfills produce methane; so trap methane and burn to produce electricity - this is useful bc methane is a more powerful source of electricity than CO2 (CON: expensive)

^^SOLUTION - eat less beef/dairy products.

ISSUE - people wouldn’t want /aren’t comfortable to make lifestyle changes

People are unlikely to change their diets.

24
Q

What is meant by a fuel?

A

A substance that release energy when combusted.

25
Q

Examples of fuel:

A
  • Coals
  • Hydrocarbons
26
Q

Most fuels contain hydrogen and carbon, suggest why this is a problem.

A

The carbon and hydrogen are oxidised.

COMPLETE COMBUSTION

This produces CO2 (and water vapour) - which is a greenhouse gas and contributes to climate change.

Eg methane, a hydrocarbon complete combustion:

COMPLETE COMBUSTION = ENOUGH OXYGEN PRESENT

CH4 + O2 -> CO2 + 2H2O

INCOMPLETE COMBUSTION
- Produces carbon monoxide (toxic, scentless and colourless - so people have CO detectors in their homes)
- Carbon and water molecules aren’t fully oxidised.
- CO binds to haemoglobin and reduces O2 transported around the body.

27
Q

How is sulfur dioxide produced?

A

Some fuels eg coal contain sulfur. When these coal is burnt the sulfur atoms are oxidised.

S(g) + O(g) -> SO2(g)

28
Q

How are oxides of nitrogen (NOx) produced?

A

Produced inside engines eg car engines.

In engines, high temp cause nitrogen in engine and oxygen in air to react.

Nitrogen molecules are oxidised to produce oxides of nitrogen (NOx).

N2 (g)+ O2 (g) -> NOx (g)

29
Q

Consequences of NOx and Sulfur dioxide:

A
  • Breathing problems in humans
  • Dissolve in rainwater to form acid rain which damage trees (less trees so more CO2) and corrode buildings made from limestone.
30
Q

How are particulate produced?

A

In incomplete combustion - from unburned hydrocarbons.

CH4 + O2 -> CO/C+ H2O

31
Q

Consequences of particulates:

A
  • They can cause damage to human health eg increase the risk of lung/heart disease.
  • The can reduce the amount of solar energy from the Sun that reaches the Earth’s surface (global dimming - which may be affecting rainfall patterns)

GCSE Chemistry (9 decks)

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