Topic 9- Chemistry of the atmosphere: Flashcards
Proportion of differnet gases in the atmospbhere:
For 200 million years the proportions of different gases have been the same:
* 80% nitrogen
* 20% oxygen
* Small proportions of other gases
The earth’s early atmosphere:
- Evidence is limited because of the huge time scale (4.6 bliion years) and theories have developed/changed over time
- At the start of this period, the atmosphere was similar to Mars or Venus (mainly C02 with little oxygen)
- Volcanoes proudced nitrogen- gradually built up in the atmosphere
- Water vapour condensed to form the oceans- carbon dioxide dissolved in the water
- Carbonates precipitated, producing sediments, also reducing the amount of carbon dioxide in the atmosphere
How did oxygen increase?
- Algae and plants produced the oxygen in the atmosphere by photosynthesis
- Algae first produced oxygen 2.7 billion years ago, soon after this, oxygen appeared in the atmosphere
- Over the next billion years, plants evolved
- The % of oxygen gradually increased- enabled animals to ‘evolve’
How did carbon dioxide decrease?
- Algae and plants absorbed carbon dioxide, decreasing the % of carbon dioxid e in the amosphere- this happend by photosynthesis
- Carbon dioxide was also decreased by the formation of sedimentary rocks that contain carbon
- The production of fossil fuels from the remains of dead plants and animals
Greenhouse gases:
- Maintain temperatures on earth high enough to ** support life**
- Include water vapour, carbon dioxide and methane
The greenhouse gas effect:
- Electromagnetic radiation at most wavelengths (long and short)
- The earth absorbs some radiation, warming us up (essential for life on earth). Howvever, some heat is radiated from the earth as infrared radiation
- Some of this IR radiation is absorbed by greenhouse gaases in the atmosphere
- The atmosphere warms up leading to greenhouse effect and global warming
Human activities contributing to an increase in greenhouse gases ibn the atmosphere:
- Driving (increases carbon dioxide)
- Consuming electricity (increases carbon dioxide)
-
Raising livestock cows (increases methane)
Many scientists believe that human activities cause the temperatutre of the earth to increase- resulting in global climate chage
Global climate change:
- Increase in global temperature- a major cause of climate change
Several potential effects, including:
1. Extinction of species
2. Rasing sea levels (melting of polar ice caps)
3. Migration (people will movve away from areas suffering a drought)
4. Decrease in crop yield
The carbon footprint and it’s reduction:
Carbon footprint: the total amount of carbon dioxide and other greenhouse gases emitted over the full life cycle of a product
* Can be reduced by reducing emissions of carbon dioxide and methane (e.g. by using less electricity) OR by limiting amount of travel/ transporatation AND by planting more trees
* However, these factors may be limited- It’s difficult, expensive, time consuming and planting trees take away land that could be used to grow crops
Atmospheric pollutants from fuels:
- Combustion- a major source of atmosphheric pollutants
- Most fuels (including coal) contain carbon, hydrogen and some sulfur
- Gases released into atmosphere when fuels burn may include: carbon dioxide, water, carbon monoxide an dnitrogen
- Solid particles and unburned hydrocarbons can be released
- Not enough oxygen- incomplete combustion, produces soot
- Complete combustion- carbon an hydrogen are oxidised- forms carbon dioxide and water
Properties and effects on atmospheric pollutants:
- Carbon monoxide: toxic gas, colourless and odourless- not easy to detect
- Sulfur dioxide: produces acid rain and respiratory problems in humans
- Particulates: cause global dimming and human health problems
Describe how deposits of natural gas were formed from fossil fuels:
- Plankton died
- It was covered by sediments
- It was subjected to high temperature and pressure over millions of years
