TOPIC 8 Earth And Atmospheric Science Flashcards
Number of carbons in a carbon chain and their names
1 meth- 2 Ethel- 3 prop- 4 But- 5 pent- 6 hex-
Homologous series
Group of compounds with the same functional group and so react in similar ways
Functional group
Group of atoms that determine how a compound generally reacts.
What do you do if there’s more than one identical functional group?
Use di- for two
Tri- for 3
Tetra for 4
Crude oil
A mixture of substances (mostly hydrocarbons of different lengths) which are separated through fractional distillation.
Where does fractional distillation take place?
In a fractionating column with a temperature gradient (coolest at top, hottest at bottom).
Where do larger hydrocarbons end up?
At the bottom of the fractionating column due to having higher bp’s.
Where do shorter hydrocarbons end up?
At the top of the fractionating column due to having lower bps.
What stops the liquid from remixing in the fractionating column?
Bubble caps make sure each fraction is separated into a mixture of hydrocarbons containing similar bps.
Saturated hydrocarbon
Hydrocarbons containing only single bonds.
Unsaturated hydrocarbons
Hydrocarbons containing double/triple bonds between carbon atoms.
Number of carbons in carbon chain in gas and its use
1-3
Used for heating and cooking
Number of carbon chains in petrol and its use
8
Used for fuel in cars
Number of carbons in chain for kerosene and its use.
15
It’s used for aircraft fuel.
Number of carbons in diesel and its use
20
Used for fuel in large vehicles
Number of carbons in chain in fuel oil and its use
40
It’s used as fuel in large ships and in power stations.
Number of carbons in chain for bitumen and its use
70+
Used in tarmac
Viscosity
Resistance of tendency to flow
Characteristics of longchain hydrocarbons
Viscous
Low ease of ignition and volatility
High bp
Volatility
Tendency of a substance to vaporise
Characteristics of short chain hydrocarbons
Low viscosity
V flammable and volatile
Low bp
Cracking
Splitting up of low in demand longchain hydrocarbons to create shorter chain hydrocarbons that are high in demand. It’s a form of thermal decomposition.
Give an example of cracking
Decane»_space; octane + ethene
How do you crack hydrocarbons in a lab
Vaporised hydrocarbons are passed over a powdered catalyst. Much energy is needed to break the bonds so cracking is carried out at 400—700 degrees Celsius .
What’s the catalyst used in cracking?
Aluminium oxide
What pressure is cracking carried out at?
70atm
Word equation/ balanced equation for complete combustion of hydrocarbons
Hydrocarbon + oxygen»_space; carbon dioxide + water
C3H8 +5O2»_space; 3CO2 +4H2O
(Much energy is also released)
Word equation for incomplete combustion of hydrocarbons
Hydrocarbon + limited oxygen»_space; carbon dioxide + carbon monoxide + water + carbon composites
Why’s carbon monoxide dangerous?
Because its colourless, odourless and sinks.
It binds to the haemoglobin in your red blood cells, replacing oxygen. This results in fainting, comas or even death. Some appliances like boilers produce this when faulty.
Why are carbon composites (soot) bad?
They cause respiratory issues and make buildings/environment dirty. Can result in industrial melanism
Acid rain
Burning of fossil fuels with sulfur impurities mean sulfur and oxygen react to form sulfur dioxide, this rises and dissolves into water in the clouds (forming sulfuric acid at a pH of roughly 4) which then falls as acid rain. This acidified lakes and soil, killing plants and animals. Erodes metals and statues/buildings. It’s even linked to some respiratory diseases.
How are nitrogen oxides formed? What are their effects?
Car engines react nitrogen and oxygen together with heat to form nitrous oxides. These cause acid rain, photochemical smog and health issues.
Reaction within hydrogen fuel cells
Hydrogen + oxygen»_space; water (+energy!!)
Advantages of hydrogen fuel cells
Is a clean fuel
Has no harmful pollutants
Obtained from water which is renewable via electrolysis of water.
Can be obtained from product.
Disadvantages of hydrogen fuel cells
Require a special and expensive engine
Needs top be manufactured via electrolysis which is expensive and uses energy from fossil fuels which produces pollutants.
Highly flammable so requires a reinforced container
Expensive to buy
What was the original atmosphere like?
We had a molten crust that was so hot that our atmosphere dispersed into space. After millions of years however, the crust cooled down and formed volcanoes. Intense volcanic for the first billion years went on to form the early atmosphere and oceans. MOSTLY CO2 AND LITTLE/NO OXYGEN.
Which planets was the early atmosphere originally like?
Venus and mars today
How did the oceans form?
Volcanic activity released nitrogen, water vapour and small parts of methane/ ammonia. The earth then cooled and condensed the water vapour to form the oceans.
Why did the CO2 decrease?
Sea absorption: sea dissolved CO2 to form carbon precipitates (sediments on seabed) and marine shells. The bodies of the marine life going to form sedimentary rock. Also algae (evolved 2.7billion years ago) and plants (1.7) photosynthesised to produce oxygen.
Why did the oxygen increase in the early atmosphere?
Photosynthesis from algae/plants
As oxygen increased, simple organisms couldn’t cope with the environmental change and so they were killed which added more oxygen to the atmosphere for more complex life to form.
This created the OZONE LAYER.
Photo synthesis word equation
Carbon dioxide + water >(light> glucose + oxygen
The glucose is stored as starch in a plant
Why is the ozone layer good?
Because it blocks out harmful UV rays from the sun, enabling evolution of more complex life.
Our atmosphere today
21% oxygen
0.03% CO2
78% nitrogen
0.9% argon
Oxygen test
If it delights a glowing splint, oxygen is present.
Greenhouse effect
The sun emits short wavelength UV radiation which reaches the earth’s surface and is absorbed and then re-emitted as long wave IR radiation. This IR is absorbed by greenhouse gases in the atmosphere (CO2, methane, water vapour).
These gases then re-radiate it in all directions, including back to earth which warms the earth’s surface. We enhance this effect by producing more greenhouse gases.
How do you investigate the proportion of oxygen in the atmosphere?
Soak iron wool in acetic acid (catalyses reaction) and put into measuring cylinder that’s inverted into a container of water. Iron reacts w oxygen so water will rise to form the oxygen’s space. Leave until the difference in water volumen in the cylinder stops changing .
100*change in volume / start volume = % of oxygen in air.
