Topic 8 - Fuels and Earth Science Flashcards by Lottie Abbott

What is a hydrocarbon

a compound containing ONLY carbon and hydrogen

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What are the compounds found in crude oil

hydrocarbons arranged in chains and are mostly alkanes.

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

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

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Why is crude oil a finite source

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

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How is crude oil separated?

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

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

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What does viscosity mean

How easily a substance flows

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what fraction of crude oil has a higher viscosity and why

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

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

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

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Which fractions of crude oil have higher boiling points

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

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What is the equation for a combustion reaction with a hydrocarbon

Hydrocarbon + oxygen&raquo_space;> Carbon Dioxide and water

C3H8 + 5O2&raquo_space;»> 3CO2 + 4H2O

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What is a homologus series

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

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What are two different homologus series of hydrocarbons?

Alkanes and Alkenes

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What does complete combustion of hydrocarbons produce

Carbon dioxide and water

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What does incomplete combustion of hydrocarbons produce

carbon monoxide and soot

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

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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How do some hydrocarbons produce sulfur dioxide in use?

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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what are the names of some pollutants responisble for acid rain

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

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Name some effects of acid rain

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

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

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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What causes photochemical smog

Nitrogen oxides (a harmful pollutants)

Name an alternative fuel for cars

Hydrogen

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

+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

What happens as a reaction in a hydrogen fuel cell

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

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

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

Define cracking

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

What happens in cracking in terms of alkanes and alkenes

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

What is thermal decomposition

one substance breaks down into new ones when heated

Are alkanes saturated or unsaturated

saturated

Are alkenes saturated or unsaturated

unsaturated

What is the difference between a saturated and unsaturated molecules

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

Why is cracking necessary

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

What is the process of cracking

- 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

How was the Earths early atmoshere formed | Phase 1

- 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

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

- the oceans dissolved the CO2 | - nitrogen gas was put into the atmosphere by ammonia reacting with oxygen and released by denitrifying bacteria

Why did levels of Nitrogen increase (phase 2)

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

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

When green plants evolved, they removed CO2 and produced O2

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

locked up in sedimentary rocks and fossil fuels

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

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

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

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

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

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

What are the names of significant greenhouse gases

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

What is the greenhouse effect

- 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

What happens when the concentration of greenhouse gases increases

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

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

- 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

Why are methane levels increasing

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

What does the enhanced greenhouse effect lead to

global warming

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

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

Why historical data of recording temperature and CO2 levels less accurate

- 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

How can we estimate past data of the earths climate and CO2 levels why is this data collection less precise

- gas bubbles in ice cores - fossils - dendrochronology (tree rings) less precise than instrumental sampling and global levels

How can we use less fossil fuels

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