Effects of combustion on the environment Flashcards
What is the difference between renewable and non-renewable fuels
Renewable fuel resources can be replaced, and will not run out: eg ethanol, methanol (made from wood, human or animal waste etc), vege oil used as fuel, biodiesel or hydrogen gas
Non-renewable fuel resources cannot be replaced once they are used up. Eg petrol, diesel, natural gas, coal and crude oil. They are the most commonly used in the world.
How are fossil fuels formed
Most non-renewable fuel resources are called fossil fuels. Fossil fuels are formed from the remains of living things. Millions of years of heat and pressure changed the remains of plants and animals into fossil fuels. Eg, coal was formed from the remains of plants. Oil and natural gas were formed from the remains of sea creatures. Fossil fuels are carbon-based compounds. This means they contain the element carbon (along with eg hydrogen and oxygen)
Outline the carbon cycle
Most of the molecules that make up living tissue contain carbon. When organisms die the carbon is recycled so that it can be used by future generations. The model that describe the processes involved is called the carbon cycle. Large amounts of carbon exist in the atmosphere as carbon dioxide (CO2). Carbon dioxide is absorbed by green plants (in ocean and on land) during the process of photosynthesis to make organic molecules such as sugars. These molecules are passed onto consumers when they eat plant material. Animals and plants release carbon dioxide back into the air as a waste product from respiration. Decomposers (eg bacteria and fungi) break down dead organic matter, releasing CO2 back into the atmosphere. Decomposers are essential because without them, all of the C on the planet would eventually become locked up in dead carcasses and other waste. In some conditions, decomposition is prevented. The plant and animal material may then be available as fossil fuel in the future for combustion. When fossil fuels are burned, carbon dioxide is released back into the air.
Describe the greenhouse effect
The Earth’s atmosphere acts like a blanket around the Earth. About 80-90% of the Earth’s natural greenhouse effect is due to water vapour, a strong greenhouse gas. The remainder is due to CO2, CH4 and a few other minor gases.
Solar radiation passes through the atmosphere
Some solar radiation is reflected by the atmosphere and the Earth’s surface
Solar radiation is absorbed by the surface, warming it. The warm surface radiates heat out as infrared radiation
Greenhouses reflect some of the infrared radiation back to Earth, making the Earth warmer.
If the Earth had no atmosphere it’d be -18°C during the day and -160° at night.
Methane released by farm animals also contribute to global warming
Balance of CO2 in the atmosphere
The amount of CO2 in the atmosphere is kept relatively constant by photosynthesis by plants and by respiration by plants and animals.
Humans beings may disturb the balance of CO2 gas in the atmosphere by burning fossil fuels - produces CO2 and by removing forests, reduces the amount of photosynthesis that can occur, and therefore less CO2 is removed from the atmosphere.
Consequences of global warming
- Ice melting in the Earth’s polar regions could cause seawater levels to rise, and some low-lying islands and shorelines could disappear below sea-level.
- Higher temps above the Earth’s surface could cause more water to evaporate from seas and lakes. May result in more frequent and severe weather events such as storms, floods sand droughts.
- Diseases that occurred primarily in tropical countries might spread to other regions.
- crop production
- loss of species due to inability to adapt fast enough to changing habitat.
Describe acid rain
When fossil fuels such as coal, oil and natural gas are burned, oxides of sulphur, carbon and nitrogen escape into the air. These molecules dissolve in the water in the clouds and make the rainwater more acidic than normal.
Fossil fuels are burnt
The impurities and oxides of carbon, sulphur and nitrogen dissolve into the rain clouds
The impurities and oxides produces acid rain due to lower pH
Consequences of acid rain
Stonework and metalwork can be corroded
Acidic water is harmful to fish and other wildlife in waterways
Acidic water stunts plant growth and kills them due to lower pH of soil
In strong sunlight, a mixture of unburnt hydrocarbon vapour and carbon monoxide with other oxides of nitrogen can lead to photochemical smog.
CO2 dissolves in water to form carbonic acid which dissolves calcium carbonate (limestone/marble):
CaCO3 + H2CO3 -> Ca(2+) + 2HCO3-
Describe ocean acidification
The world’s oceans absorb about a quarter of the CO2 that is released into the atmosphere. As CO2 increases, so do the levels in the ocean. Photosynthetic marine organisms benefit from higher CO2 conditions in the ocean, as they require CO2 to live. However, the CO2 absorbed by the ocean is changing the chemistry of the seawater by a process called ocean acidification.
The absorbed CO2 reacts with water to form carbonic acid:
CO2 + H2O -> H2CO3
This acid lowers the pH of the oceans and affects the formation of shells, corals and plankton. (Shells contain calcium carbonate) Many of these organisms play key roles in marine food chains. Without them, there could be no other marine life.
Describe pollution from internal combustion engine
The internal combustion engine uses hydrocarbons, such as petrol, diesel oil and kerosene, which burn in air. If the fuel does not burn efficiently the hydrocarbons do not undergo complete combustion. Some fuel escapes unburned, as well as the CO gas and soot that are products of incomplete combustion. Some of the energy contained the fuel goes to waste.
Explain biofuels
Ethanol can be used to fuel vehicles and for heating. It can be manufactured by fermenting plant material. Plants remove CO2 from the atmosphere and it is released again when the ethanol is combusted. In theory, this should result in no net increase of atmospheric CO2 (ie biofuels should be carbon neutral.
