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PAPER 2 : CHEMISTRY > C9 > Flashcards

C9 Flashcards

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1
Q

How long ago did the Earth form?

A

4.6 billions years

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2
Q

How was the early atmosphere formed and what was its composition?

A
  • the early atmosphere was formed from lots of intense volcanic eruption (which released a lot of gases)
  • the early atmosphere composition was mainly CO2, there was also a lot of water vapour (which later formed oceans), some nitrogen which has built up over time, a little bit of methane and ammonia, and hardly any oxygen
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3
Q

How do we know this was the composition? Why can’t we be sure? What do we base our assumptions on?

A

We don’t, scientists think the Earth’s early atmosphere was similar to the atmospheres found on Mars and Venus today. That is, lots of carbon dioxide and very little oxygen

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4
Q

Describe the composition of the atmosphere today

A

for the last 200 million years:

  • about 4/5 (80%) of nitrogen
  • 1/5 (20%) of oxygen
  • and small proportions of various other gases (eg: CO2, water vapour & noble gases)
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5
Q

How did the oceans form?

A
  • due to the heat from the volcanoes, the water vapour in the atmosphere cooled below 100oC
  • and condensed into liquid water this formed oceans
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6
Q

How did the oceans forming change CO2 levels? Where did the carbon in the carbon dioxide go to next?

A
  • ocean forming made CO2 levels decreased as most of the CO2 would overtime dissolve into the ocean(as carbon dioxide can dissolve in water)
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7
Q

Where did the carbon in the carbon dioxide go to next?

A
  • the dissolved CO2 ended up being used by sea creatures to build their shells
  • when they died their shells ended up as sediments, which now forms carbonate rocks, such as limestone
  • we say the carbon has been “locked up”
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8
Q

How did the level of oxygen increase?

A
  • first algae then plants (over the next billion years) evolved and started to carry out photosynthesis
  • oxygen is of product
  • this % of oxygen gradually increased due to it being released into the atmosphere allowing the animals to evolve
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9
Q

Write the word and symbol equations for this process(photosynthesis)

A

6CO2 + 6H20 → C6 H12 O6 +6O2
→ = photosynthesis

carbon dioxide + water → glucose + oxygen

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10
Q

How did the level of carbon dioxide fall?

A
  • algae & plants decreased the % of CO2 in the atmosphere by carrying out photosynthesis. CO2 is a reactant in the photosynthesis chemical reaction
  • CO2 was also decreased by it dissolving into the ocean and the formation of sedimentary rocks & fossil fuels that contains carbon
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11
Q

Why are GHG essential for our survival?

A

they keep temperatures on Earth high enough to support life

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12
Q

Give 3 examples of greenhouse gases

A

Carbon dioxide, methane and water vapour

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13
Q

Describe the Greenhouse Effect

A

1) radiation reaches us from the sun (shorter wavelengths such as visible light and UV light) and enters the atmosphere
2) a lot of this radiation is absorbed by the Earth’s surface, then re-emitted as longer wavelength infrared
3) some of the heat radiates back into space
4) while some of it is absorbed by a layer of greenhouse gases (water vapour, CO2 and methane), then re-emitted, warming up the Earth – this is called The Greenhouse Effect

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14
Q

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

A
  • the radiation from the sun enters our atmosphere at a short wavelength
  • it is absorbed by the Earth’s surface & re-emitted at a longer wavelength
  • the infrared radiation is absorbed by GHG then re-emitted in all direction causing an increase in global temperature
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15
Q

Name 2 human activities which increase the amount of carbon dioxide in the atmosphere

A
  • burning fossil fuels (when fueling up our cars)

- deforestation (as when trees are cut down the removal of CO2 decrease)

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16
Q

Name 2 human activities which increase the amount of methane in the atmosphere

A
  • paddy fields (rice field)

- cattle farming (cow burps)

17
Q

What effect do most scientists believe humans will have on the temperature of the planet/ and believe this will cause?

A
  • humans will increase the temperature of the planet

- which would go on to cause climate change

18
Q

What do scientists base their views on?

A

they base their views on evidence that has been peer-reviewed

19
Q

What challenges do many scientists face when trying to collect and present their evidence?

A
  • because the climate is a complex system it is difficult to model future climate
  • also the media may not present ALL the facts so their articles can be bias
20
Q

Describe 4 effects of climate change

A
  • sea levels rising + ice caps melting
  • extinction/ deforestation
  • drought (extreme weather)
  • famine
21
Q

What is the definition of carbon footprint?

A

is the total amount of CO2 and other GHG emitted over the full life cycle of a product, service or event

22
Q

How we can reduce our carbon footprint and why this is difficult?

A
  • use better insulation
  • use renewable energy
  • increase recycling
  • carbon capture
  • personal choice
23
Q

What is the major cause of atmospheric pollution?

A

combustion of (fossil) fuels

24
Q

Name 5 gases which can be released into the air when fuels are burned

A
  • carbon dioxide
  • water vapour
  • carbon monoxide
  • sulfur dioxide
  • nitrogen oxide (NO, NO2, NO3)
25
Q

Give 2 other sources of atmospheric pollutants

A
  • unburned hydrocarbons

- particulates of soot (carbon)

26
Q

Name the 2 types of combustion and a brief description of the difference

A
  • complete combustion = has lots of oxygen

- incomplete combustion = it doesn’t have enough oxygen

27
Q

How is carbon dioxide produced?

A

complete combustion: methane + oxygen → carbon dioxide + water

CH4 + 2O2 → CO2 + 2H2O

28
Q

How is carbon monoxide produced?

A

incomplete combustion = where there has not been enough oxygen

methane + oxygen → carbon dioxide + water
2CH4 + 3O2 → 2CO + 4H2O

29
Q

How are carbon particulates (soot) produced?

A

incomplete combustion = where there is very little oxygen

methane + oxygen → carbon (soot) + water
CH4 + O2 → C + 2H2O

30
Q

How is sulfur dioxide produced?

A

incomplete combustion = where sulfur impurities combine with oxygen to form sulfur dioxide

sulfur + oxygen → sulfur dioxide
S + O2 → SO2

31
Q

How are nitrous oxides produced?

A

incomplete combustion = high temperatures in cars which allows the nitrogen and oxygen to react

first: nitrogen + oxygen → nitrogen monoxide
N2 + O2 → 2NO

then: nitrogen monoxide + oxygen → nitrogen dioxide
2NO + O2 → 2NO2

32
Q

EXAMPLE QUESTION:

Methane is burned in a boiler which has a partially blocked air inlet pipe. Predict the products which are formed. Explain my answer

A
  • because the pipe is partially blocked, less oxygen get through
  • so incomplete combustion takes place
  • products that could be formed are: carbon monoxide, water vapour & carbon particulates
33
Q

EXAMPLE QUESTION:

Fossil fuels such as oil are made of hydrocarbons with some sulphur impurities. Predict the products which are formed in an oil-fired power station. Explain my answer

A
  • complete combustion takes place, releasing carbon dioxide & water vapour
  • sulfur impurities also reacts with oxygen making sulfur dioxide
  • if temperature were high enough, some oxides of nitrogen may form
34
Q

Explain the problems with carbon dioxide, water vapour and carbon monoxide

A
  • they are all caused by the burning of fossil fuel

- carbon monoxide is a toxic gas and is not easily detected due to being odorless

35
Q

Explain the problems with sulfur dioxide and nitrogen dioxide

A
  • they both cause acid rain

- which damages trees and buildings and respiratory problems in humans

36
Q

Explain the problems with particulates

A
  • unburned hydrocarbons can make buildings dirty

- and worsen breathing difficulties and cause global dimming

PAPER 2 : CHEMISTRY (3 decks)

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