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Chemistry GCSE > C6 - Global Challenges > Flashcards

C6 - Global Challenges Flashcards

1
Q

Methane:

A
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2
Q

Ethane

A
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3
Q

Propane

A
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4
Q

Butane

A
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5
Q

Define a ‘hydrocarbon’

A

A compound made up of only hydrogen and carbon atoms

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6
Q

Define a ‘homologous series’

A

A group where each compound has the same general formula with each successive member differing by CH2. All compounds have the same properties.

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7
Q

General formula of alkanes?

A

CnH2n+2

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8
Q

How do alkanes react?

A

They react in a process called combustion.

Complete combustion:

Alkane + O2 –> CO2 + H2O

2C2H6 + 7O2 —> 4CO2 + 6H2O

Incomplete combustion:

Alkane + O2 –> CO + H2O

2C2H6 + 5O2 —> 4CO + 6H2O

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9
Q

What is crude oil?

A

It is a fossil fuel.

It is a non-renewable resource - it is being used up faster than it is being formed

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10
Q

How is crude oil formed?

A

They are formed from the remains of dead organisms that lived millions of years ago - chemical reactions over time turned them into crude oil

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11
Q

How do we separate crude oil?

A

Using fractional distillation

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12
Q

What are alkenes?

A

A homologous series of hydrocarbons with at least one carbon-carbon double bond

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13
Q

General formula of alkenes?

A

CnH2n

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14
Q

What is the functional group for alkenes?

A

C=C

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15
Q

Define a ‘functional group’

A

An atom or group of atoms which give a molecule its chemical properties

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16
Q

How do you test for alkenes?

A
  1. React bromine water with the alkene
  2. Mixture should turn colourless if alkenes are present
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17
Q

What is ‘cracking’?

A

Cracking is a chemical process which converts large alkanes into smaller alkanes and alkenes

For example:

C7H16 –> C2H4 + C5H12

Heptane –> ethene + pentane

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18
Q

What are the typical conditions for cracking?

A

High temperature (600-700°)

Hot catalyst of alumina or silica

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19
Q

Why is cracking done?

A

Smaller hydrocarbons are more useful to use as:

  • They have lower boiling points
  • They flow more easily
  • They are easier to ignite

Cracking also helps the supply to meet the demand

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20
Q

What are ‘addition polymers’?

A

They are made from an additon reaction in which molecules join together to make 1 big molecule

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21
Q

What are the first four alcohols?

A

Methanol

Ethanol

Propanol

Butanol

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22
Q

What are the first four alkanes?

A

Methane

Ethane

Propane

Butane

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23
Q

What are the first three alkenes?

A

Ethene

Propene

Butene

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24
Q

General formula of alcohols?

A

CnH2n+1OH

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25
Q

What is the functional group for alcohols?

A

OH

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26
Q

Ethene

A
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27
Q

Propene

A
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28
Q

Butene

A
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29
Q

Methanol

A
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30
Q

Ethanol

A
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31
Q

Propanol

A
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32
Q

Butanol

A
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33
Q

How do alcohols react with metals?

A

Ethanol + Sodium –> Sodium Ethoxide + Hydrogen

2C2H5OH + 2Na –> 2C2H5ONa + H2

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34
Q

Combustion of alcohols:

A

Complete:

ethanol + oxygen —> carbon dioxide + water

2C2H5OH + 6O2 —> 4CO2 + 6H2O

Incomplete:

ethanol + oxygen —> carbon monoxide + water

C2H5OH + 2O2 —> 2CO + 3H2O

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35
Q

What observations do you see when an alcohol reacts with a metal?

A
  • Bubbles
  • White solid formed if fully evaporated
  • Slow, less vigorous reaction
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36
Q

How do alcohols oxidise?

A

They oxidise to a type of molecule called a carboxylic acid. This is accompanied by a colour change.

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37
Q

Functional group of a carboxylic acid:

A

COOH

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38
Q

Methanoic acid

A
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39
Q

Ethanoic acid

A
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40
Q

Propanoic acid

A
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41
Q

Butanoic acid

A
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42
Q

How are carboxylic acids formed?

A

They are formed when an alcohol oxidises to produce water and a carboxylic acid

e.g.
Ethanol + oxidising agent —-> Ethanoic acid + water

C2H5OH + 2[O] —> CH3COOH + 2H2O

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43
Q

General formula of carboxylic acids

A

CnH2nO2

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44
Q

Ethyl Ethanoate:

A
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45
Q

Crude Oil Fractionating column:

A
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46
Q

Functional group of esters

A

COO

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47
Q

How is crude oil separated by fractional distillation?

A

The oil is heated until most of it has turned into gas.

The gases enter a fractionating column, (the liquid parts, bitumen, are drained off)

In the column, there is a temperature gradient (it is hot at the bottom and gets gradually cooler)

The longer hydrocarbons have higher boiling points. They turn back into liquids and drain out of the column early on, when they are near the bottom.

The shorter hydrocarbons have lower boiling points. They turn to liquid and drain out much later on, near the top.

Finally, the crude oil mixture is separated out into different fractions. Each fraction contains a mixture of hydrocarbons, mostly alkanes, with similar boiling points.

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48
Q

How are esters formed?

A

Esters are made by reacting alcohols with carboxylic acids in the presence of a sulfuric acid catalyst

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49
Q

How to draw an ester:

A
  1. Remove OH from the acid
  2. Remove H from alcohol
  3. Join remaining pieces together
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50
Q

Drawing condensation polymers:

A
  1. Remove double bond
  2. Extend bonds either side
  3. Add brackets
  4. Write ‘n’ outside the brackets
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51
Q

Condensation vs Addition Polymers

A

Addition:

1 monomer always

1 functional group

No bi-products

Condensation:

1 or 2 monomers

2 functional groups

Usually water formed

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52
Q

What is the functional group for amines?

A

NH2

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53
Q

What is hydrogenation?

A

It is when alkenes are reacted with hydrogen. The hydrogen reacts with the double-bonded carbons and adds across the double bonds.

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54
Q

How does a chemical cell work?

A
  1. They have two halves
  2. One half of the cell is losing electrons - oxidation
  3. The other half is gaining electrons - reduction
  4. The electrons flow from the first half to the second half, producing a current
  5. This continues until the reactants are used up
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55
Q

What is a fuel cell?

A

A fuel cell produces electrical energy efficiently from an exothermic reaction

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56
Q

How does a hydrogen-oxygen fuel cell work?

A

Hydrogen-oxygen fuel cells use hydrogen as their fuel.

  1. When oxygen or air are supplied, the hydrogen and oxygen react together to produce water - 2H2 + O2 -> 2H2O
  2. The energy released in the reaction is used to produce a potential difference
  3. This causes current to flow when the fuel cell is connected in a circuit
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57
Q

What happens at the anode in a hydrogen-oxygen fuel cell?

A

Hydrogen molecules lose electrons at the anode and become hydrogen ions:

H2 –> 2H+ + 2e-

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58
Q

What happens at the cathode in a hydrogen-oxygen fuel cell?

A

When hydrogen ions reach the cathode, they combine with oxygen and electrons from the electrical circuit.

4H+ + O2 + 4e- –> 2H2O

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59
Q

Advantages of a hydrogen-oxygen fuel cell:

A
  • High efficiency
  • Theoretically zero emission
  • No harmful waste products
  • Uses renewable sources of energy
  • Lightweight and compact
  • No moving parts
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60
Q

Disadvantages of a hydrogen-oxygen fuel cell:

A
  • Often uses poisonous catalysts
  • The method used to produce the hydrogen for the fuel cells uses fossil fuels which produce pollutants
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61
Q

Why is ammonia important?

A

Ammonia is an important raw material in making fertilisers

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62
Q

What nutrients are needed by plants?

A
  • Nitrogen
  • Phosphorous
  • Potassium
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63
Q

What are the signs of mineral deficiency?

A

Poor growth, discoloured leaves

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64
Q

What form do the nutrients need to be in in order to be absorbed by the plants?

A

They need to be in a water-soluble form (i.e. ions)

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65
Q

What are the typical ions in NPK fertilisers?

A

NO3- - provides nitrogen

NH4+ - provides nitrogen

PO43- - provides phosphorus

K+ - provides potassium

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66
Q

What is the definition of a fertiliser?

A

Fertlisers are substances that replace the elements used by plants as they grow

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67
Q

How are fertilisers made?

A

Most fertilisers are made by reacting ammonia, which is a base, with an acid, to make a salt which contains at least one of the essential elements.

e.g. Ammonia + Sulfuric acid –> Ammonium Sulfate

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68
Q

What are the raw materials for the Haber Process

A

Air, natural gas, steam

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69
Q

What temperature is used in the Haber Process?

A

450oC

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70
Q

What pressure is used in the Haber Process?

A

200 atmospheres

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71
Q

What catalyst is used in the Haber Process?

A

An Iron catalyst

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72
Q

What product is produced in the Haber Process?

A

Ammonia - NH3

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73
Q

What are the raw materials in the Contact Process?

A

Sulfur, air, water

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74
Q

What temperature is used in the Contact Process?

A

450oC

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75
Q

What pressure is used in the Contact Process?

A

2 atmospheres

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76
Q

What catalyst is used in the Contact Process?

A

Vanadium Oxide catalyst

77
Q

What product is produced in the Contact Process?

A

Sulfuric acid

78
Q

Why is a low pressure used in the Contact Process?

A

A low pressure is used as the equilibrium position is already pushed to the right.

There is no need for a high pressure, since 2 atmospheres is just enough to push the gases through the converter.

79
Q

What is the chemical formula for the Haber Process?

A

N2 + 3H2 ⇔ 2NH3

80
Q

What is the purpose of the Haber Process?

A

The Haber Process is used to manufacture ammonia from hydrogen and nitrogen.

Ammonia is an important raw material in making fertilisers

81
Q

How is nitrogen produced for the Haber Process?

A

Nitrogen is produced by the fractional distillation of liquefied air

82
Q

How is hydrogen produced for the Haber Process?

A

Hydrogen is manufactured by reacting natural gas (methane) with steam

83
Q

What is the first stage of the Contact process?

A

Sulfur + Oxygen –> Sulfur dioxide

S + O2 –> SO2

84
Q

What is the second stage of the Contact process?

A

Sulfur dioxide + Oxygen ⇔ Sulfur trioxide

2SO2 + O2 ⇔ 2SO3

85
Q

What is the third stage of the Contact process?

A

Sulfur trioxide + Water –> Sulfuric acid

SO3 + H2O –> H2SO4

86
Q

Define a batch process

A

A series of operations which are carried out over a period of time

87
Q

Define a continuous process

A

A process in which the product comes out without interruptions and not in groups

88
Q

Define an ore

A

An ore is a rock or a mineral that contains enough metal to make it economical to extract the metal

89
Q

What compound is copper extracted from?

A

Copper is extracted from copper(II) sulfide

90
Q

How is copper extracted?

A

It is extracted from copper (II) sulfide in two stages:

Stage 1 - Copper (II) sulfide is heated in air to produce copper oxide and sulfur dioxide

Stage 2 - Copper (II) oxide is heated with carbon to form copper and carbon dioxide

91
Q

What is the chemical formula for stage 1 during the extraction of copper?

A

2CuS + 3O2 –> 2CuO + 2SO2

92
Q

What is the chemical formula for stage 2 during the extraction of copper?

A

2CuO + C –> 2Cu + CO2

93
Q

How is iron extracted?

A

Iron is extracted from its ore using a blast furnace

94
Q

What raw materials are used in the extraction of iron?

A

Iron ore

Coke (carbon)

Limestone

95
Q

What is the first reaction that takes place in the extraction of iron?

A

The coke burns:

C + O2 –> CO2

96
Q

What is the second reaction that takes place in the extraction of iron?

A

The limestone thermally decomposes:

CaCO3 –> CaO + CO2

97
Q

What is the third reaction that takes place in the extraction of iron?

A

The carbon dioxide reacts with more coke:

CO2 + C –> 2CO

98
Q

Why is carbon dioxide reacted with more coke?

A

To make it into a better reducing agent

99
Q

How is iron formed in the extraction of iron?

A

The carbon monoxide reduces the iron ore to iron metal:

Fe2O3 + 3CO –> 2Fe + 3CO2

100
Q

What is the calcium oxide used for in the extraction of iron?

A

The calcium oxide combines with the impurities to form the liquid slag:

CaO + SiO2 –> CaSiO3

101
Q

Why can you not extract aluminium in the same way you can extract copper or iron?

A

It cannot be extracted like iron or copper as it is more reactive than carbon

102
Q

How is aluminium extracted?

A

Through electrolysis

103
Q

Why is the electrolysis of aluminium oxide difficult?

A

Electrolysis only works if the compound is in solution or if it is molten - however aluminium oxide does not dissolve in water and its melting point is very high.

104
Q

How is aluminium oxide electrolysed?

A

First, it must be dissolved in molten cryolite which has a much lower melting point of 950ºC.

The molten mixture is contains in a large electrolysis cell made from steel lined with graphite.

During the process:

  • Aluminium is produced at the cathode
  • Oxygen is produced at the anodes
105
Q

What acts as the cathode in the electrolysis of aluminium oxide?

A

The graphite lining

106
Q

What acts as the anode in the electrolysis of aluminium oxide?

A

A series of large graphite blocks

107
Q

What is the overall equation in the extraction of aluminium?

A

2Al2O3 –> 4Al + 3O2

108
Q

What is the half equation for the reaction that occurs at the cathode during the extraction of aluminium?

A

Al3+ + 3e- –> Al

109
Q

What is the half equation for the reaction that occurs at the anode during the extraction of aluminium?

A

2O2- –> O2 + 4e-

110
Q

What is a high grade ore?

A

An ore that contains many metal ions

111
Q

What is a low grade ore?

A

An ore that contains very little metal ions

112
Q

What is bioleaching?

A

Bioleaching is a method of extraction using bacteria.

The bacteria break the bonds between the copper and sulfide ions.

Once broken, copper atoms are formed.

113
Q

What are the benefits of bioleaching?

A

The benefits of bioleaching is that it is cheaper than traditional mining and processing.

It also allows metals to be extracted from ores that contain too little metals.

It also does not release harmful sulfur dioxide into the atmosphere

114
Q

What are the disadvantages of bioleaching?

A

It is much slower than traditional methods.

Toxic substances are sometimes produced which need to be treated carefully.

115
Q

What is phytoextraction?

A

It is the process of plants taking up metal ions from the soil, and then being burnt in order to retrieve the metal compounds

116
Q

How is copper extracted through phytoextraction?

A

Some plants take up copper metals from the soil.

Once the copper has been taken up and stored by the plant, it is burnt.

Once burned, copper oxide is left.

This is impure so it is electrolysed in order to form pure copper

117
Q

What are the benefits of phytoextraction?

A

It is cheaper than traditional mining and processing.

It produces less waste and involves smaller energy transfers

It is also closer to being a carbon-neutral activity that can contribute to sustainable development

118
Q

What are the disadvanatges of phytoextraction?

A

It is quite slow.

Crops may need replanting and harvesting for several years before the available metal is removed from the soil.

119
Q

What is an alloy?

A

An alloy is a mixture of two or more elements, at least one of which is a metal

120
Q

What metals are used to make steel?

A

Mainly iron as well as smaller amounts of other metals and carbon

121
Q

What metals are used to make duralumin?

A

Aluminium and copper

122
Q

What metals are used to make solder?

A

Tin and copper

123
Q

What metals are used to make brass?

A

Copper and zinc

124
Q

What metals are used to make bronze?

A

Copper and tin

125
Q

What are the typical uses for steel?

A

Buildings, bridges, cars

126
Q

What are the typical uses for duralumin?

A

Aircraft parts

127
Q

What are the typical uses for solder?

A

Joining electrical components and copper pipes

128
Q

What are the typical uses for brass?

A

Musical instruments and coins

129
Q

What are the typical uses for bronze?

A

Bells, propellers for ships

130
Q

What are the overall properties of steel?

A

High tensile strength, hard, tough, durable, resistant to corrosion

131
Q

What are the overall properties of duralumin?

A

Strong, light-weight, malleable, good conductor of heat and electricity

132
Q

What are the overall properties of solder?

A

Ductile, good conductor of heat and electricity

133
Q

What are the overall properties of brass?

A

Low-friction, malleable

134
Q

What are the overall properties of bronze?

A

High resistance to corrosion, brittle, high melting point

135
Q

What is corrosion?

A

Corrosion is the reaction of a metal with substances in its surroundings. E.g. oxygen and water

136
Q

What is rust?

A

Rust is a specific type of corrosion which only happens to iron.

It is a redox reaction

137
Q

What is the reaction for the process of rusting?

A

Iron + Oxygen + Water –> Hydrated Iron (III) Oxide

4Fe + 3O2 + 2H2O –> 2Fe2O3•H2O

138
Q

What are the methods used to prevent corrosion?

A
  • Painting
  • Coating with oil, grease or plastic
  • Plating with zinc (galvanising)
  • Plating with tin
139
Q

How is zinc used to plate iron?

A

Iron is dipped in molten zinc to coat the iron.

It acts as a physical barrier between the iron and the air.

Since zinc is more reactive than iron, it will sacrifice itself to protect the iron if damaged.

140
Q

What is sacrificial protection?

A

When a more reactive metal is used as plating and thus sacrifices itself if there is damage.

141
Q

How is tin used to plate iron?

A

It is coated by electroplating.

It acts as a physical barrier between the iron and the air

Since it is less reactive, the iron will react first if the tin is damaged.

142
Q

Definition of strength

A

The ability to withstand a force/load

143
Q

Definition of Hardness

A

The ability to resist scratching/denting

144
Q

Definition of Durability

A

The ability to function correctly whilst lasting a long time

145
Q

Definition of Brittle

A

When an object shatters when enough force is applied

146
Q

Definition of Flexible

A

How much you can bend an object when a force is applied

147
Q

Definition of Malleable

A

How much you can hammer an object into shape without it breaking

148
Q

Definition of Compressive strength

A

How well an object can resist a force when being squashed

149
Q

Definition of Tensile strength

A

How well an object can resist a force when being stretched

150
Q

Definition of Density

A

How much mass is in a given volume

151
Q

Definition of Lightweight

A

An object with low density

152
Q

What is a composite material?

A

A composite material is 2 or more materials combined of which each has different properties

153
Q

Examples of composite materials

A

Fibreglass

Carbon Fibre

Reinforced concrete

154
Q

Describe fibreglass/carbon fibre

A

Made from glass/carbon fibres and resin

Resin is durable but not strong

Fibres have low density and a high tensile strength

Thus fibreglass/carbon fibre is lightweight, strong and hard

155
Q

Describe reinforced concrete

A

Made from steel bars and concrete

Concrete has a high compressive strength

Steel has a high tensile strength

156
Q

What is a life cycle assessment?

A

A ‘cradle to grave’ assessment of the impact of making, using and disposing of a manufactured product

157
Q

Examples that are considered in a life cycle assessment:

A

Sustainability

Enironmental impact

Life span of the product

Recycling possibility

158
Q

Why recycle?

A

Lower costs when recycling

Prevents it going to landfill

Some materials have a finite source

159
Q

What are the considerations when debating whether to recycle a product or not?

A

Is it low cost?

Does it use a lot of energy?

Is it at a high quality once recycled?

How limited are the raw materials?

How difficult is it to sort before recycling?

160
Q

What are the steps when recycling metals?

A

Collecting and transporting the used metals to a recycling centre

Breaking up and sorting the different metals

Removing impurities from the metals

They are then melted by heating and the molten metal is poured into moulds to produce new blocks called ingots

161
Q

How is paper recycled?

A

Paper is mixed with water, cleaned, and then rolled and heated to make new paper

162
Q

How is glass recycled?

A

Glass is melted by heating and moulded into new glass objects

163
Q

What are the two methods used to recycle polymers?

A

Open-loop recycling

Closed-loop recycling

164
Q

What is open loop recycling?

165
Q

What is closed loop recycling?

166
Q

What are the three main gases in the atmosphere?

A

Nitrogen - 78%

Oxygen - 21%

Argon - 0.9%

167
Q

How was Earth’s early atmosphere formed?

A

It is likely it was formed from substances released by volcanoes

During the early years, there was a great deal of volcanic activity. They released huge volumes of water vapour and carbon dioxide.

The water vapour condensed to form oceans, leaving an atmosphere of mostly carbon dioxide

168
Q

How has an oxygen-rich atmosphere developed over time?

A

Plants and algae had grown and they make their own food through photosynthesis.

They absorb carbon dioxide from the atmosphere and release oxygen.

169
Q

What is the greenhouse effect?

A

Greenhouse gases such as carbon dioxide and methane absorb infrared radiation radiated by the Earth’s surface, then emit it in all directions

170
Q

What are the different steps in the greenhouse effect?

A
  1. Energy transferred by radiation from the Sun reaches the Earth’s surface
  2. The radiation warms up the Earth’s surface
  3. Infrared radiation is emitted by the Earth’s surface. Some goes directly into space. Some is absorbed by greenhouse gas molecules in the atmosphere
  4. Greenhouse gas molecules emit infrared radiation in all directions, warming the Earth’s surface and atmosphere
171
Q

What is the enhanced greenhouse effect?

A

The release of additional greenhouse gases by human activities has the potential to cause an enhanced greenhouse effect, increasing the temperature of the Earth’s atmosphere.

172
Q

How can greenhouse gas emissions be reduced?

A

By:

  • Reducing the consumption of fossil fuels, for example by using biofuels
  • Using renewable energy sources such as wind and solar energy to generate electricity
  • Stopping carbon dioxide escaping when fuels are used by using carbon capture
173
Q

What are pollutants?

A

Substances released into the environment which may harm living things

174
Q

How is carbon monoxide formed?

A

From the incomplete combustion of carbon based fuels

175
Q

How are carbon particulates formed?

A

From the incomplete combustion of carbon based fuels

176
Q

Why do acidic oxides cause problems?

A

Normally the main gases in air, nitrogen and oxygen, do not react.

However they do react at high temperatures in vehicle engines forming nitrogen monoxide, which is oxidised in air to form nitrogen dioxide.

Nitrogen dioxide dissolves in the moisture in clouds, forming an acidic solution, which eventually falls as acid rain.

177
Q

How is carbon monoxide removed from the air?

A

By using alternatives to fossil fuels

178
Q

How are carbon particulates removed from the air?

A

By using alternatives to fossil fuels

179
Q

How is sulfur dioxide removed from the air?

A

Power stations can use scrubbers which cleans the gases passing through the smokestack.

180
Q

How are NOx gases removed from the air?

A

Catalytic converters in cars turn nitrogen monoxide into nitrogen

181
Q

What are NOx gases?

A

Nitrogen monoxide and nitrogen dioxide

182
Q

What is potable water?

A

Water which is safe to drink

183
Q

What are the 3 main requirements for potable water?

A

Must have a low level of dissolved substances

Must have a pH between 6.5-8.5

No microorganisms

184
Q

What are the three sources of water?

A

Fresh water - groundwater, surface water

Salt water - seawater

Waste water - sewage water

185
Q

How is fresh water treated?

A

There are three stages in filtering fresh water:

  • Filtration
  • Sedimentation
  • Sterilisation

Firstly, a coarse filter is used to remove any large objects.

Then, it gets passed onto the next tank where the waste sits onto the floor (sedimentation)

Next, a fine filter is used to remove any fine grains.

Finally, chlorine is added to sterilise the water where it is then stored in a tank.

186
Q

How is waste water treated?

A

Waste water treatment is very similar to fresh water treatment except bacteria are used.

Firstly, a coarse filter is used to remove any large objects.

Then, it gets passed onto the next tank where the waste sits onto the floor (sedimentation). The sludge left on the floor is sent to tanks to be decomposed by anaerobic bacteria

Next, a fine filter is used to remove any fine grains. Aerobic bacteria are used to remove any organic waste.

Finally, chlorine is added to sterilise the water where it is then stored in a tank.

187
Q

What are the two methods used to treat salt water?

A

Reverse osmosis

Distillation

188
Q

How is salt water treated using distillation?

A

The mixture is heated until the water evaporates out the tank.

It then passes through a large condensation tube where it condenses into pure water.

189
Q

How is salt water treated using reverse osmosis?

A

Pressure is applied to salt water where it then passes through a partially permeable membrane where only water molecules can pass through.

Filtered water remains.

Chemistry GCSE (6 decks)

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