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A - Chemistry GCSE > Topic 8 - Fuels and Earth Science > Flashcards

Topic 8 - Fuels and Earth Science Flashcards

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1
Q

What is a hydrocarbon

A

a compound containing ONLY carbon and hydrogen

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2
Q

What are the compounds found in crude oil

A

hydrocarbons arranged in chains and are mostly alkanes.

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3
Q

What is the importance of crude oil for the petrochemical industry?

A

Its a raw material used to create lots of useful substances such as fuel for aircrafts

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4
Q

Why is crude oil a finite source

A

because it is made from plants and animals under high temperatures and will eventually run out

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5
Q

How is crude oil separated?

A

Fractional Distillation-

  • fractions of crude oil are separated in fractionating column by their different boiling and melting points
  • In the column there’s a temperature gradient (cold at top)
  • longer hydrocarbons have higher boiling points like bitumen so they drain out at the bottom of the column where its hottest
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6
Q

What are the names and uses of some fractions from crude oil

A 
Gases- domestic heating and cooking
Petrol- cars
Kerosene- Aircrafts
Diesel- larger vehicles
Fuel Oil - ships
Bitumen- Roads
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7
Q

What does viscosity mean

A

How easily a substance flows

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8
Q

what fraction of crude oil has a higher viscosity and why

A

Bitumen because it is thick like treacle and has a longer chain of hydrocarbons

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9
Q

Which fractions of crude oil are easier to ignite and why?

A

Shorter chains like gases because they have lower boiling points and react with oxygen which can burst into flames

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10
Q

Which fractions of crude oil have higher boiling points

A

longer molecules like bitumen because forces are much stronger between the big molecules

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11
Q

What is the equation for a combustion reaction with a hydrocarbon

A

Hydrocarbon + oxygen&raquo_space;> Carbon Dioxide and water

C3H8 + 5O2&raquo_space;»> 3CO2 + 4H2O

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12
Q

What is a homologus series

A

family of molecules which have the same general formula and share similar chemical properties

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13
Q

What are two different homologus series of hydrocarbons?

A

Alkanes and Alkenes

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14
Q

What does complete combustion of hydrocarbons produce

A

Carbon dioxide and water

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15
Q

What does incomplete combustion of hydrocarbons produce

A

carbon monoxide and soot

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16
Q

Why are the products or incomplete combustion and why are they dangerous

A

Carbon monoxide in form of Soot

toxic carbon monoxide - binds to red blood cells and stops oxygen being carried around the body leads to comas death or fainting
soot- makes buildings black and reduces air quality

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17
Q

How do some hydrocarbons produce sulfur dioxide in use?

A

When fossil fuels are burned they release mostly CO2 but can also release other harmful gases such as sulfur dioxide or nitrus oxides

sulfur dioxide (SO2) comes from sulfur impurities in the fossil fuels

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18
Q

what are the names of some pollutants responisble for acid rain

A

sulfur dioxide mixing with clouds to make it dilute and fall as acid rain

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19
Q

Name some effects of acid rain

A

lakes become acidic so animals die
kills trees
damages limestone buildings
stone statues too

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20
Q

Why are oxides of nitrogen produced when fuels are burning in engines

A

Nitrogen oxides are produced by a reaction between oxygen and nitrogen in the air caused by the energy released in combustion reactions
eg) internal combustion engines in cars

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21
Q

What causes photochemical smog

A

Nitrogen oxides (a harmful pollutants)

22
Q

Name an alternative fuel for cars

A

Hydrogen

23
Q

Why would hydrogen be a good/ bad alternative and renewable fuel

A

+very clean
+no pollutants
+efficient energy source

  • expensive
  • hydrogen gas has to be manufactured which costs
  • uses energy from another source which creates pollutants
  • hard to store (explosive) and not widely available
24
Q

What happens as a reaction in a hydrogen fuel cell

A

hydrogen combines with oxygen to produce energy and the only waste product is water

25
Q

Where does the hydrogen come from for a hydrogen fuel cell (which makes it renewable)

A

water
but also as the only waste product is water in the hydrogen oxygen reaction we can obtain hydrogen again through electrolysis

26
Q

Define cracking

A

breaking down of longer less useful chains of hydrocarbons to make smaller more useful ones to fit demand

27
Q

What happens in cracking in terms of alkanes and alkenes

A

turns long saturated alkane molecules into smaller more useful unsaturated alkenes and alkane molecules

28
Q

What is thermal decomposition

A

one substance breaks down into new ones when heated

29
Q

Are alkanes saturated or unsaturated

A

saturated

30
Q

Are alkenes saturated or unsaturated

A

unsaturated

31
Q

What is the difference between a saturated and unsaturated molecules

A

A unsaturated molecule has a double bond which means that it can make more bonds as the double bond can open up

whereas saturated molecules already have all bonds formed

32
Q

Why is cracking necessary

A

It helps meet supply in demand

Bitumen is in a much higher supply than demand so if broken down can become more useful fractions such as petrol which has more demand than supply

33
Q

What is the process of cracking

A
  • vaporised hydrocarbons are passed over powdered catalyst at 400-700 degrees at 70 atmospheres
  • An aluminium oxide catalyst is used
  • long chain molecules “crack” on surface of catalyst
34
Q

How was the Earths early atmoshere formed

Phase 1

A
  • The earths surface cooled and a thin crust formed
  • volcanos kept erupting and releasing gases
  • degassing produced CO2 (also steam, methane, amonnia)
  • Then when it settled the earths atmosphere was mainly CO2 and water vapour and not much oxygen
  • this water vapour condensed to form oceans
35
Q

How did the formation of oceans influence the composition of the atmosphere (phase 2)

A
  • the oceans dissolved the CO2

- nitrogen gas was put into the atmosphere by ammonia reacting with oxygen and released by denitrifying bacteria

36
Q

Why did levels of Nitrogen increase (phase 2)

A

Because N2 isnt very reactive and amount increased because it isnt broken down

37
Q

Why did photosynthetic organisms change the composition of the earths atmosphere (phase 2)

A

When green plants evolved, they removed CO2 and produced O2

38
Q

Where did most of the CO2 end up (phase 2)

A

locked up in sedimentary rocks and fossil fuels

39
Q

What did the build up of oxygen in the atmosphere lead to? (phase 3)

A

killed off organisms that couldnt tolerate it and allowed the evolution of more complex organisms that used oxygen

40
Q

What does the ozone layer (O3) do? (phase 3)

A

blocked harmful rays from the sun so more complex organisms could evolve

41
Q

What are the proportions of gases in the Earths atmosphere now?

A

78% nitrogen
21% oxygen
1% is all other gases including CO2

42
Q

What are the names of significant greenhouse gases

A

CO2 , methane, water vapour, sulfur dioxide, nitrus oxides

43
Q

What is the greenhouse effect

A
  • The earth radiates heat as IR radiation
  • IR is absorbed by greenhouse gases
  • Some of the earths radiation is reflected back to earth by greenhouse gases and some is re-emitted into space
  • absorbtion and reflection which keeps the earth warm
44
Q

What happens when the concentration of greenhouse gases increases

A

it leads to the enhance greenhouse effect where less radiation is re-emitted to space and short wave radition from the sun is absorbed in heating our atmosphere

45
Q

How do human activities lead to increase in the concentration of greenhouse gases

A
  • Larger population respiring gives out more CO2
  • More people means more energy for cooking and heating and transport
  • More countries are becoming industrialised
  • More burninhg of fossil fuels releases CO2
  • Deforestation leads to less CO2 being taken out of the atmosphere
46
Q

Why are methane levels increasing

A

-produced in digestive process of livestock such as sheep and cows

47
Q

What does the enhanced greenhouse effect lead to

A

global warming

48
Q

What does global warming lead to and what happens as a cause of it

A

Climate change-
changes rainfall patterns
icecaps are melting so sea levels rise

49
Q

Why historical data of recording temperature and CO2 levels less accurate

A
  • because its taken in fewer location in the world unlike now its taken all over the world
  • and going back more there is no data for CO2 levels which means we dont have enough data to prove global warmng is caused by CO2
50
Q

How can we estimate past data of the earths climate and CO2 levels

why is this data collection less precise

A
  • gas bubbles in ice cores
  • fossils
  • dendrochronology (tree rings)

less precise than instrumental sampling and global levels

51
Q

How can we use less fossil fuels

A

deduce CO2 emissions small scale - by cycling walking places more or getting a smart meter for your home

large scale- industries become more efficient and invest in renewable energy

A - Chemistry GCSE (11 decks)

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