Page 16 - 1202 Question Bank Chemistry Form 5 KSSM

(b) Glucose molecules combined to form starch and releasing simple molecules such as water.
CH OH CH OH CH OH
2 2 2
C O C O C O
HO OH H OH H OH
H H H
C C C C C C
OH H OH H OH H
H H HO H HO H
C C C C C C
H OH H OH H OH
Glucose
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CH OH CH OH CH OH
2 2 2
C O C O C O
H H H H H H H H H
C C C C C C + H O
OH H OH H OH H 2
O O O O
C C C C C C
H OH H OH H OH
Starch
11. Synthetic polymers are very stable. Unlike metals, 7. To produce vulcanised rubber in the school laboratory,
wood or paper, they do not rust, rot or decay easily in strips of rubber are soaked in disulphur dichloride
the presence of water, oxygen or other chemicals or in solution in toluene then dried in air.
sunlight. 8. Vulcanised rubber:
12. Synthetic polymers are widely used in medicine,
C C C C
packaging, coating, textile, electrical and electronic
industry, adhesive, household items and others. S S S S Sulphur
13. Effects of using synthetic polymers on the S S S S cross
C C linkage
environment: C C C C
(a) Synthetic polymers are not biodegradable S S
Rubber
(not decayed by microorganism) so when S S
polymer chain
accumulated, able to block drainage and caused C C
C C C C
flash floods.
(b) When synthetic polymers are burnt, poisonous (a) Sulphur atoms form cross linkages between
gases are produced. the long chains of rubber polymers.
(b) Sulphur cross linkages prevent the long
4.2 Natural Rubber chain of rubber polymers from sliding over
each other easily.
1. Latex is a milky liquid that drips out when incisions (c) Sulphur cross linkages also help the rubber
are made on the bark of the rubber tree trunk, process polymer chains get back to their original
call “tapping”. form after stretching.
2. Latex is a type of coloid that consist of rubber particles (d) Used: to manufacture tyres, rubber hose
and water. and gloves
3. Natural rubber is a natural polymer formed from
monomers called isoprene or 2-methylbut-1,3-diene. Vulcanised rubber Unvulcanised rubber
H CH H H H CH H H Can withstand high Cannot withstand high
3 3
temperatures temperatures
n C C C C C C C C
H H H H n More elastic Less elastic
Isoprene Polyisoprene
(natural rubber) Harder and stronger Less hard, softer
4. Natural rubber polymer is known as polyisoprene has Can resist oxidation Easily oxidised
a formula (C H ) with n valued at as much as 10 000.
5 8 n
5. Latex coagulates in the presence of acid while 4.3 Synthetic Rubber
ammonia solution prevents coagulation of latex.
6. To produce vulcanised rubber in industry, natural 1. Synthetic rubber is man-made polymer produced
rubber is heated with sulphur and zinc oxide as the from polymerisation process of hydrocarbon obtained
catalyst. from fractions of petroleum.

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