Page 56 - ACE YR IGCSE A TOP APPROACH TO CHEM

(b) Glucose [1] 9 B
The linkage part is at C=C double bond.
(c) Light provides energy. [1]
10 B
(d) Endothermic [1] In addition polymerisation, only one type of monomer
The energy taken in to break bonds is greater than is used, which is an alkene. Alkenes contain C=C double
the energy given out to form bonds. bonds that allow addition polymerisation to happen.
Energy is taken in. [1] In condensation polymerisation, two or more monomers
are used. Different monomers will have different
(e) The rate of reaction increases. [1] functional groups. So, there will be more than one
Light provides energy. [1] functional group in the polymers.
Carbon dioxide and water gain enough energy
to react. [1] Part 2: Structured Questions
1 (a) X: Gasoline / petrol [1]
11 Organic Chemistry Y: Paraffin / kerosene [1]
(b) (i) For cooking [1]
Part 1: Multiple-choice Questions (ii) For making chemicals / plastics [1]

1 A (iii) Waxes / polishes / oil for machinery [1]
Naphtha is a raw material for producing chemicals. (iv) For making tar road [1]
2 A When molecules are large, the fractions
Alkenes can decolourise bromine water from orange to become less runny. It changes from gas at
colourless. the top to solid at the bottom. They are less
An alkene has the general formula of C H . C H and C H flammable. Therefore, the last two fractions
n
2n
3
6
2
4
are alkenes. are not used as fuels.
3 C (c) (i) Contain only [1]
Cracking is the process of breaking down bigger hydrogen and carbon [1]
molecules into smaller molecules and alkenes. (ii) Alkanes have all C–C single bonds. [1]
To get an alcohol, water is added to the alkenes. It is Alkenes have one C=C double bond. [1]
called hydration.
(iii) Add bromine water [1]
4 C Alkane: no change / orange [1]
Hydrogen is a type of fuel that will not produce carbon
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Alkene: decolourised / becomes colourless

dioxide. Water is the only product in the burning of [1]
hydrogen. Bromine water is in orange.
5 A H H H H
The general formula for alkenes is C H . Therefore, the
2n
n
empirical formula should be CH . C C + Br Br Br C C Br
2
6 C H H H H
S and U are alcohols. They are from the same homologous Dibromoethane
series.
R is ethene. 2 (a) The remains of plants and animals that lived
S is ethanol. millions of years ago [1]
T is propanoic acid. can be burned to generate energy [1]
U is propanol.
The fossil fuels are petroleum, coal and natural gas.
7 D (b) Methane [1]
O (c) (i) A family of similar compounds that have
C O the same functional group, so they have
CH 3 CH 2 CH 3
similar chemical properties. [1]
From the structure, the right side of the ester is from a (ii) Any three from: [3]
monomer called methanol. • Same functional group
The left side of the ester is from a monomer called • Same general formula
propanoic acid. • Consecutive members differ by CH
In the naming of an ester, the first part of the name is • Same method of preparation 2
from alcohol and the second part is from carboxylic acid.
Therefore, this ester is called methyl propanoate. • Different physical properties
• Different chain lengths
8 A Note: Can be similarities or differences.
Both nylon and protein are polyamide. They have amide (d) (i) A hydrogen atom in a molecule is replaced
linkage. by a halogen atom. [1]

Cambridge IGCSE TM
168 Ace Your Chemistry

Answers.indd 168 3/4/22 3:54 PM