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GCSE - Chemistry > Topic 7 > Flashcards

Topic 7 Flashcards

1
Q

What atoms do hydrocarbons contain?

A

hydrogen and carbon atoms

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2
Q

What is a hydrocarbon?

A

A hydrocarbon is any compound that is formed from carbon and hydrogen atoms only.

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3
Q

What kind of bonds do alkanes have?

A

all alkanes have single bonds

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4
Q

What are alkanes?

A

Alkanes are the simplest type of hydrocarbon you can get. They are a homologous series - a group of organic compounds that react in a similar way.

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5
Q

What is the general formula for alkanes?

A

CnH2n+2

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6
Q

What type of compounds are alkanes?

A

saturated compounds - each carbon atoms form 4 single covalent bonds.

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7
Q

What are the names of the first 4 alkanes and their formulas?

A

Methane = CH4
Ethane = C2H6
Propane = C3H8
Butane = C4H10

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8
Q

What does the length of the hydrocarbon chains change?

A

The properties of the hydrocarbon.

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9
Q

What are the properties of a short carbon chain?

A

The shorter the carbon chain, the more runny, volatile and flammable a hydrocarbon is.

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10
Q

What do the properties of hydrocarbons affect?

A

how they’re used in fuels e.g. short chain hydrocarbons with lower boiling points are used as ‘bottled gases’ - stored under pressure as liquids in bottles.

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11
Q

When does the complete combustion of any hydrocarbon happen?

A

When there is plenty of oxygen

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12
Q

What does the complete combustion of any hydrocarbon release?

A

lots of energy

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13
Q

What is the waste products of the complete combustion of any hydrocarbon?

A

carbon dioxide and water vapour

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14
Q

What happens in the complete combustion of any hydrocarbon?

A

both carbon and hydrogen from the hydrocarbon are oxidised

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15
Q

What are hydrocarbons used as and why?

A

hydrocarbons are used as fuels due to the amount of energy released when they combust completely.

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16
Q

What is the word equation for the complete combustion of hydrocarbon?

A

hydrocarbon + oxygen —> carbon dioxide + water

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17
Q

What is crude oil?

A

a fossil fuel that is a mixture of lots of different hydrocarbons most of which are alkenes

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18
Q

How is crude oil formed?

A

from the remains of plants and animals, mainly plankton, that died millions of years ago and were buried in mud. Over millions of years, with high temperature and pressure, the remains turn to crude oil, which can be drilled up from the rocks where it’s found.

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19
Q

What are non renewable fuels?

A

fuels that are being used up faster than they can be made

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20
Q

What are some examples of non renewable fuels?

A

fossil fuels like coal oil and gas

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21
Q

What are finite recourses?

A

resources that are one day going to run out

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22
Q

What can fractional distillation be used for?

A

to separate hydrocarbon fractions

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23
Q

How does fractional distillation work?

A

1)The oil is heated until most of it has turned into gas. The gases enter a fractionating column and the liquid is drained off.
2)In the column there’s a temperature gradient it’s hot at the bottom and get’s cooler as you go up
3)The longer hydrocarbons have high boiling points. They condense back into liquids and drain out of the column early on, when they’re near the bottom. The shorter hydrocarbons have lower boiling points. They condense and drain out much later on, near the top of the column where it’s cooler.
4)You end up with the crude oil mixture separated out into different fractions. Each fraction contains a mixture of hydrocarbons that all contain a similar number of carbon atoms, so similar boiling points.

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24
Q

Name the alkene molecules found in the fractions from coolest to hottest and the approximate number of carbons.

A

LPG (liquefied petroleum gas) ~3 carbons cool
Petrol ~8 carbons
Kerosene ~15 carbons
Diesel oil ~20 carbons
Heavy fuel oil ~40 carbons very hot

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25
What does the petrochemical industry use some of the hydrocarbons from crude oil for?
as a feedstock to make new compounds for use in things like polymers, solvents, lubricants and detergents.
26
What are oil the products you get from crude oil an example of?
organic compounds -compounds that contain carbon atoms
27
Why do you get such a large variety of products from crude oil?
carbon atoms can bond together to form different groups called the homologous series. These groups contain similar compounds with many properties in common.
28
What are the names of families found in the homologues series?
alkenes and alkanes
29
What is cracking mean?
splitting up long-chain hydrocarbons
30
What type of reaction is cracking?
cracking is a thermal decomposition reaction - breaking molecules down by heating them
31
Why are short chain hydrocarbons more useful than long chain hydrocarbons?
Short-chain hydrocarbons are flammable so make good fuels and are high in demand. Long-chain hydrocarbons form thick gloopy liquids like tar which aren't all that useful so a lot of the longer alkane molecules produced from fractional distillation are turned into smaller, more useful ones by a process called cracking.
32
What types of hydrocarbons does cracking produce?
alkanes and alkenes
33
What are alkenes used as?
a starting material when making lots of other compounds and can be used to make polymers
34
Explain catalytic cracking?
1)Heat long-chain hydrocarbons to vaporise them 2)Then the vapour is passed over a hot powdered aluminium oxide catalyst. 3)The long-chain molecules split apart on the surface of the specks of catalyst.
35
Explain steam cracking?
vaporise the hydrocarbons, mix them with steam and then heat them to a very high temperature.
36
What is the general word equation for cracking?
long-chain hydrocarbon --> short-chain hydrocarbon + alkene
37
What is the difference between alkanes and alkenes?
Alkanes have a C-C single bond and alkenes have a C=C double bond. Alkenes are more reactive than alkanes and react with bromine water, which is used as a test for alkenes.
38
What does the C=C double bond mean for alkenes?
that alkenes have two fewer hydrogens compared with alkanes containing the same number of carbon atoms. This makes them unsaturated
39
What happens if the C=C double bond in alkenes opens up?
it makes a single bond, allowing the two carbons to bond to other atoms. This makes alkenes reactive - far more reactive than alkanes
40
What is the general formula for alkanes?
C H n 2n
41
What are the names of the first 4 alkanes and their formulas?
Ethene = C C 2 4 Propene = C H 3 6 Butene = C H 4 8 Pentene = C H 5 10
42
How do alkenes react with oxygen?
In a large amount of oxygen, alkenes combust completely to produce only water and carbon dioxide. However, there isn't enough oxygen in the air for this so when you burn them they tend to undergo incomplete combustion. Carbon dioxide and water are still produced but you can get carbon and carbon monoxide which are poisons.
43
What is the word equation for complete combustion of alkenes in oxygen?
alkene + oxygen ---> carbon dioxide + water
44
What is the word equation for incomplete combustion of alkenes in oxygen?
alkene + oxygen ---> carbon + carbon monoxide + carbon dioxide + water
45
How are incomplete and complete combustion of the same alkene of the same compound different?
incomplete combustion results in a smoky yellow flame and less energy being released compared to complete combustion
46
What is a functional group?
a group of atoms in a molecule that determine how that molecule typically reacts
47
What is the functional group for alkenes?
C=C so they all react in similar ways
48
Most of the time how do alkenes react?
addition reactions - the carbon=carbon double bond will open to leave a single bond and a new atom is added to each carbon
49
What is hydrogenation?
addition of hydrogen
50
What is also present in an addition reaction between an alkene and hydrogen?
an alkene is reacted with hydrogen in the presence of a catalyst
51
What happens in an addition reaction between an alkene and hydrogen?
hydrogen reacts with the double bond of the alkene to open it up and form the equivalent, saturated alkane
52
What happens when steam reacts with an alkene?
water is added across the double bond and an alcohol is formed
53
How can ethanol be made?
By mixing ethene with steam and then passing it over a catalyst. After the reaction has taken place, the reaction mixture is passed from the reactor into a condenser. Ethanol and water have higher boiling points than ethene, so both condense whilst any unreacted ethene gas is recycled back into the reactor. The alcohol can be purified from the mixture by fractional distillation.
54
What do 2 bromine and 1 ethene form when they react together?
dibromoethane
55
What is the test for alkenes and explain what happens?
-The addition of bromine to a double bond When orange bromine water is added to a saturated compound like an alkane, no reaction will happen and it'll stay bright orange. If it's added to an alkene the bromine will add across the double bond, making a colourless dibromo-compound so the bromine water is decolourised.
56
What are plastics made up of?
long-chain molecules called polymers
57
What are polymers?
long molecules formed when lots of small molecules called monomers join together. This reaction is called polymerisation.
58
What conditions does polymerisation need?
high pressure and a catalyst
59
What are addition polymers made?
from unsaturated monomers
60
What bonds do the monomers that make up addition polymers have?
double covalent bonds
61
What are addition polymers made from?
unsaturated monomers
62
What is addition polymerisation?
lots of unsaturated monomers molecules (alkenes) can open up their double bonds and join together to form polymer chains
63
How do you find the name of the polymer?
from the type of monomer it is made from just stick poly in the front so propene becomes poly(propene)
64
What is the function groups for alcohols?
-OH and end in -ol
65
What is the general formula for an alcohol?
C H OH n 2n+1
66
What is the formula for the first 4 alcohols in the homologous series?
methanol = CH OH 3 ethanol = C H OH 2 5 propanol = C H OH 3 7 butanol = C H OH 4 9
67
What are the properties of the first four alcohols?
-flammable -undergo complete combustion in air to produce carbon dioxide and water -soluble in water -react with sodium to form hydrogen -can be oxidised by reacting with oxygen to produce carboxylic acid
68
What can alcohols be used as?
Solvents and fuels. They are used as solvents because they can dissolve most things water can dissolve, but they can also dissolve substances that water can't dissolve
69
How can ethanol be made?
by fermentation which use an enzyme in yeast to convert sugars into ethanol
70
Where does the reaction to produce ethanol occur?
in solution so the ethanol produced is aqueous
71
What is the formula that produces ethanol?
sugar ------> ethanol + carbon dioxide yeast
72
When does fermentation happen the fastest?
at a temperature of around 37 degrees, slightly acidic solution and under anaerobic conditions (no oxygen)
73
What happens if the conditions for fermentation aren't right?
the enzyme could be denatured (destroyed) or could work at a much slower rate
74
What is carboxylic acid?
a homologous series of compounds and their names end in -anoic acid
75
What is carboxylic acids functional group?
-COOH
76
What is the formula for the first 4 carboxylic acids?
methanoic acid = HCOOH ethanoic acid = CH COOH 3 propanoic acid = C H COOH 2 5 butanoic acid = C H COOH 3 7
77
How does carboxylic acid react with carbonates?
like any other acid to produce salt, water and carbon dioxide. The salts formed in these reactions end in -anoate
78
How does carboxylic acid react in water?
It dissolves in water. When they dissolve, they ionise and release H+ ions resulting in an acidic solution. But, because they don't ionise completely, they just form weak acidic solutions. This means they have a higher pH than aqueous solutions of strong acids with the same concentration
79
What is the functional group for esters?
-COO-
80
What are esters formed from?
alcohol and carboxylic acid
81
What is the word equation for an ester?
alcohol + carboxylic acid ----------------> ester + water acid catalyst
82
What are some ways polymers can be made?
addition polymerisation and condensation polymerisation
83
What is polymerisation?
a process in which monomers are chemically bonded together to form a polymer, which is a long chain of repeating units
84
What is a monomer?
small organic molecules
85
What does condensation polymerisation involve and what happens when they react?
Monomers with two functional groups. When these types of monomers react they join together, usually losing small molecules such as water
86
What are the simplest polymers are produced from?
two different monomers with two of the same functional groups on each monomer
87
How is addition and condensation polymerisation different in terms of the number of types of monomers?
addition polymerisation - only has one monomer type containing C=C double bonds condensation polymerisation - has two monomer types each containing two of the same functional group or one monomer type with two different functional groups
88
How is addition and condensation polymerisation different in terms of the number of products?
addition polymerisation - only one product formed condensation polymerisation - two types of product, the monomer and a small molecule
89
How is addition and condensation polymerisation different in terms of the functional groups involved in polymerisation?
addition polymerisation - C=C double bond in monomer condensation polymerisation - two reactive groups on each monomer
90
What are the functional groups of amino acids?
amino - NH 2 carboxyl - COOH
91
What are proteins?
polymers of amino acids
92
How can proteins be made?
Different amino acids can be combined in the same chain to produce proteins
93
What is polypeptides?
polymers formed from amino acids via condensation polymerisation
94
How do amino acids form polymer chains?
The amino group of an amino acid can react with the acid group of another to make polymer chain. For every knew bond that is formed a molecule of water is lost.
95
What can one or more long-chains of polypeptides also be known as?
proteins
96
What does DNA contain?
genetic instructions that allow the organism to develop and operate
97
What is the structure of DNA?
double helix
98
What is nucleotides?
two polymer chains of monomers which make up DNA
99
What does each nucleotide contain?
a small molecule known as a base - there are four different bases known by their initials as A,C,G,T.
100
What happens when simple sugars react together?
they react together through polymerisation reactions to form larger carbohydrate polymers
101
What is a sugar and what is it made of?
small molecules that contain carbon, oxygen and hydrogen

GCSE - Chemistry (10 decks)

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