Chemistry C1

Air Quality

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C1A The Air

Air : a mixture of gases made up of small molecules with large gaps in between. 
Molecules: group of atoms joined together
Atmosphere: layer of gases surrounding the Earth 15km thick. 

What gases are found in the air?
Nitrogen: 78%
Oxygen 21%
Argon ,1%
Carbon Dioxide 0.04% - has helped keep Earth warm to support life
How are gases artificially released into atmosphere?
Human activity has also released gases into the atmosphere which affect air quality that we breathe and as air is made up of gases, air can travel and affect other parts of the world

How are gases naturally released into the atmosphere? 
volcanoes release sulfur dioxide, CO2, CO, NO2, H2O and particulates(as smoke/ash) which are small enough to stay suspended in air.

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C1B Early atmosphere

What was atmosphere on Earth first like and how did it change?
The atmosphere was mostly CO2 and water vapour. Volcanoes probably released these gases and some nitrogen and methane. Temperatures then began to cool and water vapour condesnsed to form oceans. Some of the CO2 was dissolved into the oceans or trapped in sedimentary rocks. Now the atmosphere is mostly oxygen and nitrogen with very little CO2.

how do scientists find out about early atmosphere of Earth?
Scientists can use indirect evidence such as:
-CHEMICAL COMPOSITION OF ROCKS which if they can date back to when formed , this can tell them about earlier atmospheric gases
-FOSSILS EVIDENCE OF EARLY LIFE because plant fossils shows how oxygen levels would have increased for photosynthesis and CO2 levels decreased. A lot of CO2 was trapped underground as coal/oil (fossil fuels)
-IRON PYRITE(iron sulfide) only forms if there is no oxygen present
-AIR BUBBLES IN TRAPPED ICE shows composition of air from years ago but not far enough for the earliest atmosphere.  

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C1C Air pollutants

What is a air pollutant ?
a harmful chemical(contaminates air)which directly harms our health or indirectly harms our enviro.They can change the composition of the atmosphere

Pollutant:
Sulfur dioxide         --> reacts with water + oxygen to make acid rain which                                                   damages buildings and plants
Carbon Monoxide  -->  toxic gas displacing oxygen in blood and can worsen                                                  heart conditions
Carbon dioxide      -->  rise to global warming. dissolves in rain/sea water + used                                         by plants for photosynthesis
Nitrogen monoxide-->  reacts with oxygen to form Nitrogen dioxide
Nitrogen Dioxide   -->  reacts with water+oxygen to contribute to acid rain and                                              causes breathing problems and worsen asthma
particulates           -->  blackens and dirties surfaces and if breathed in can                                                  damage lungs and make lung infections or asthma worse
water                      -->  not a pollutant 

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C1C2

How can you find out about air quality?
automatic instruments(monitors) record data of the concentration- amount of pollutants in certain volume of air. The higher the concentration the poorer the quality. The lower the concentration-the higher the quality

What influences air quality?
weather-pollutants are mixed up and wind carries pollutants in the air for miles

sources -[human acitivity]-industry, vehicles, power stations  

how are levels of nitrogen dioxides influenced?
If there is heavy traffic then higher concentrations of nitrogen dioxide contained in exhaust emissions are released. 

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C1D Measuring air pollutants

How and why is air wuality monitored?
Air pollutants are measured by using networks of monitoring stations. This information is useful for:
- individual wanting to know about the air quality of their area
-government to know whether pollutants are reachign dangerous levels anywhere
-scientists to use this data for checking their proposed explainations such as 'how do polluatns travel' etc...
Why might you get different results when measuring sometimes?
-you used equipment differently
-differences in equipment itself
Why take more than one reading?
several measurements increase ACCURACY showing how close a result is to the TRUE VALUE 
What is a best estimate and what does range show?
B.E= MEAN value of results. The smaller a range the closer you are to your true value+ increase confidence in B.E. Outliers exlucded in both

 

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C1D + C1E Formation of Air Pollutants

C1D:What does comparing ranges show?
If two ranges are overlapping it means both could have the same true value
If two ranges don't overlap, it shows a real difference

c1e: what happens when fuel burns in power stations?
any change forming a new chemical is a chemical change or chemical reaction
coal-fired power station:coal is made of carbon so Carbon + Oxygen --> CO2
gas-fired power station:hydrocoarbon so methane+oxygen-->CO2 + water
What are other products from burning fuels+ how are some formed?
sulfur dioxide : fuel contains sulfur
particulates: unburned pieces of carbon
carbon monoxide:combustion takes place in limited supply oxygen
nitrogen monoxide: forms when nitrogen in air reacts with oxygen at higih temperatures from furnace
what is an oxidation reaction?
reaction where oxygen is added to a chemical
What happens when fuel burns in a car engine?
O2+N2(AIR) +HYDROCARBON(FUEL)-->CO2,H20,N2,CO,NO,C(exhaust fumes) 

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`C1F combustion

What happens to atmos during combustion?
atoms of the reactants are rearranged to make products. 

What is needed for a combustion reaction?

  • fuel
  • oxygen
  • source of heat 

What is the word equation for combustion?
carbon + oxygen --> carbon dioxide
what is the chemical equation for combustion?
C + O --> CO2 

Why is the chemical equation better than word?
because it tells you how many atoms and molecules are involved and what happened to each atom 

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C1G conservation of atoms/mass

What is the conservation of atoms?
all atoms present at the beginning of the reaction are present at the end. None are destroyed or made, they are conserved. after a chemical reaction atoms have just been rearranged to make new chemicals

What is the conservation of mass?
all atoms have a mass and as the atoms are conserved, so is the mass.
The mass of reactants = the mass of products

How do properties of reactants and products change?
 because the atoms have combined differently, the properties of the new chemical made will be different. 
e.g.
sulfur : yellow brittle solid
oxygen: colourless, odourless gas
sulfur dioxide: colourless, choking smell, dissolves in water to form acid  

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C1H air quality and our health

What is a correlation?
when an outcome increases/decreases as a particular factor increases or decreases so there is a link between this factor and an ouctome
What is a cause?
an increase in two things can sometimes be caused by a third factor that wasn't measured OR it could be a coincidence.
What can trigger asthma attacks?
stress, dust, pollen, air pollution, colds and flu
Why do scientists publish their data + explanations?
so that other scientists can evaluate critically  at the way scientists describe methods of investigation, their presentation and interpretation of data to come to a conclusion. Also some data is hard to interpret so different scientsits can come up with different explanations.
What are repeatable results?
many measurements carried out under same conditions- produce same results 
What are reproducible results?measurements carried out under different conditions-produce same results

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C1I Improving air quality

How can you reduce pollutants from cars?
- use vehicles less
-use public transport
-MOT tests cars with emissions above legal limits not allowed on roads and checked regularly
-efficient engines so less fuel burnt for the same distance reduces pollutants and the need to buy so much fuel
-catalytic converters fitted to exhaustion pipes. Waste gases go through metal honeycomb structure with large surface area and  speeds up chemiclal reaction. harmful pollutants are converted into less harmful gases.

e.g. Carbon monoxide +oxygen --> carbon dioxide
      nitrogen monoxide --> nitrogen + oxygen 
what is a reduction reaction?
oxygen is removed from a chemical like with nitrogen monoxide in a catalytic conv.
What is a disadvantage of catalytic converters?
 carbon dioxide is still released

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C1I2 Cleaner Transport + pollutants in power stati

How to make transport cleaner?
-diesel fuels contain small sulfur compounds which can be removed and so less sulfur dioxide emissions in exhausts.
-biofuels are renewable alternative to fossil fuels
-some crars can be powered electric batteries rather than petrols.No waste gases+pollutants released,but electricity is made in PS+have to be recharged 
How can you reduce sulfur dioxide emissions from power stations?
-remove sulfur from fuels(natural gas and oil)before they are burnt
- wet scrubbing : removing sulfur dioxide from waste/flue gases before it escapes the chimmey. As sulfur dioxide is acidic gas, an alkali can be used to neutralise the sulfur dioxide.
e.g. seawater: flue gases are sprayed with seawater droplets which absorb and react with sulfur dioxide and droplets are collected and removed so clean flue gases exit chimney
OR  powdered lime(calcium oxide) + water to make an alkaline slurry which is sprayed on flue gases and reacts to form solid chemical clacium sulfate which is collected, removed and can be used a building plaster. 

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C1I3 Particulates

How can particulates be removed from power stations?
by passing them through an electrostatic precipitator containing electrically charged plates. Particulates pick up a negative charge and are attractive to the positive plate and so are collected and them removed. 

scientists interpreting data?
scientists interpret data differently leading them to come up with different explanations. Sometimes new information can disprove an explanation and scientists have to rethink about the data.  

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