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Chemistry > Topic 8 - Fuels And Earth Science > Flashcards

Topic 8 - Fuels And Earth Science Flashcards

1
Q

What are hydrocarbons?

A

Compounds that contain carbon and hydrogen only

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2
Q

What is crude oil?

A

A complex mixture of hydrocarbons containing molecules in which carbon atoms are in chains or rings.
It’s an important source of useful substances and a finite resource.

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3
Q

How is crude oil separated into simpler + more useful mixtures?

A

By fractional distillation- oil is heated until most has turned into gas. Gases enter fractionating column. In column there’s temperature gradient. Longer hydrocarbons with HBP turn back into liquids + drain out column near bottom. Shorter hydrocarbons turn to liquid + drain out near top where it’s cooler.

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4
Q

What are the 6 fractions separated from crude oil?

A 
Gases
Petrol
Kerosene
Diesel oil
Fuel oil
Bitumen
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5
Q

What is the acronym for the 6 fractions?

A

Glamorous People Keep Dogs For Babies

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6
Q

What are the uses of gases?

A

Used in domestic heating + cooking

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7
Q

What are the uses of petrol?

A

Used as a fuel in cars

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8
Q

What is the uses of kerosene?

A

Used as a fuel in aircraft

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9
Q

What are the uses of diesel oil?

A

Used as a fuel in sound cars and larger vehicles eg trains

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10
Q

What are the uses of fuel oil?

A

Used as a fuel for large ships and in some power stations

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11
Q

What are the uses of bitumen?

A

Used to surface roads and roofs

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12
Q

What are the properties of shorter hydrocarbons?

A

Intermolecular forces break a lot more easily therefore have lower BP
Easy to ignite so usually gases at room temp
Low viscosity and are much runnier

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13
Q

What are the properties of longer hydrocarbons?

A

Strong intermolecular forces therefore have high BP
Hard to ignite
Liquids at room temp
High viscosity + thick

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14
Q

What is a homologous series?

A

Series of compounds which have the same general formula. Differ by CH2 in molecular formulae from neighbouring compounds. Show a gradual variation in physical properties. Have similar chemical properties.

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15
Q

What do complete combustion reactions of hydrocarbons produce?

A

Carbon dioxide + water. Energy is given out.

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16
Q

Explain what the incomplete combustion of hydrocarbons can produce

A

Carbon and carbon monoxide due to lack of oxygen.

17
Q

How does carbon monoxide act as a toxic gas?

A

It can combine with red blood cells + stop your blood from carrying oxygen around the body. This cane lead to fainting, coma or death

18
Q

What are the problems caused by incomplete combustion?

A

Particles of carbon can be released into atmosphere. When they fall back to ground they deposit themselves as soot on buildings. Reduces air quality leading to respiratory problems.

19
Q

Explain how impurities in some hydrocarbon fuels result in the production of sulfur dioxide

A

When fossil fuels are burned they release sulfur dioxide (SO2) which comes from the sulfur impurities in the fossil fuels.

20
Q

How is acid rain caused?

A

When sulfur dioxide mixes with clouds is forms dilute sulfuric acid which falls as acid rain.

21
Q

What are the problems with acid rain?

A

Causes lakes to become acidic + plants + animals die. Also kills trees and damages limestone buildings

22
Q

What are the non renewable fossil fuels obtained from crude oil?

A

Petrol, kerosene, diesel oil + methane found in natural gas.

23
Q

Why are nitrogen oxides produced when fuels are burned in engines?

A

Caused by the internal combustion of engines in cars - nitrogen + oxygen in air react.

24
Q

What is bad about nitrogen oxides being produced from engines?

A

They’re harmful pollutants - can contribute to acid rain + photochemical smog which is air pollution that can cause breathing difficulties

25
Q

What are the advantages of hydrogen being used instead of petrol in cars?

A

Very clean
Only waste product is water
Obtained from water which is renewable

26
Q

What are the disadvantages of using hydrogen instead of petrol in cars?

A

Need a special expensive engine
Expensive to manufacture + uses energy from another source
Hard to store + not widely available
Very reactive

27
Q

What is cracking?

A

breaking down of larger, saturated hydrocarbon molecules (alkanes) into smaller, more useful ones, some of which are unsaturated (alkenes)

28
Q

Why is cracking used/necessary?

A

Lots of the longer molecules produced from fractional distillation are cracked into smaller ones as there’s more demand for products like petrol + diesel than bitumen + fuel oil

29
Q

What formed the earths early atmosphere?

A

Gases like CO2, steam, methane + ammonia produced by volcanic activity

30
Q

What was the earths early atmosphere thought to contain?

A

Little/no oxygen as there wasn’t any plants
Large amount of CO2 + water vapour from volcanoes erupting
Small amounts of other gases (methane + ammonia)

31
Q

How did the condensation of water vapour form oceans?

A

As the earth started to warm up the water vapour evaporate, cooled + condensed to create clouds which then rained down + formed oceans.

32
Q

How did the amount of CO2 in atmosphere decrease?

A

Lots of CO2 dissolved into the oceans

33
Q

How did the amount of oxygen in the atmosphere increase?

A

Primitive plants photosynthesised + removed CO2 + produced oxygen. Oxygen gradually built up and much of the CO2 got locked in fossil fuels + sedimentary rocks.

34
Q

Describe the chemical test for oxygen

A

Take a glowing splint and place it into a test tube. If it relights oxygen is present.

35
Q

What is the greenhouse effect?

A

1- earth radiates some heat radiation as infrared radiation (IR)
2- some IR absorbed by greenhouse gases
3- some IR is reflected back to Earth by greenhouse gases
4- some IR is re emitted to space
5- absorption + reflection of IR by greenhouse gases is what keeps Earth warm

36
Q

What are greenhouse gases?

A

Gases in atmosphere that absorb + reflect heat radiation. Present in small amounts. Carbon dioxide, methane + water vapour are 3 gg

Chemistry (15 decks)

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