1) Fats are composed of fatty acid molecules bonded to glycerol, while fatty acids are long chain carboxylic acids. Oils are mostly unsaturated and liquid at room temperature, while fats are saturated and solid. Unsaturated fats can be changed to saturated through hydrogenation, adding hydrogen in the presence of a nickel catalyst. 2) Natural rubber is a polymer of the monomer isoprene. Its properties include being white, elastic, soft and heat sensitive. Latex coagulation occurs when acid or air exposure allows rubber particles to overcome repulsion and collide, entangling to coagulate. Vulcanization crosslinks rubber molecules with sulfur to improve elasticity, strength and heat resistance

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Max marks
= /70
Carbon compounds
Quiz 5 on Fats and Natural Rubber with answers
Name ………………………………………………….class…………………………teacher……………………………….
Answer the following questions
1) FATS
a) What is the difference between a fat molecule and a fatty acid molecule?( 4 m)
…………………………………………………………………………………………………………………..
…………………………………………………………………………………………………………………..
…………………………………………………………………………………………………………………..
…………………………………………………………………………………………………………………..
b) Fill in the table below to list differences between oils and fats.( 6 marks)
Oils Fats
Mostly unsaturated fat Saturated fats
a)
b)
c)
c) Explain how unsaturated fats can be changed to saturated fats? ( 6 marks)
• ………………………………………………………………..

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• ………………………………………………………………..
• ………………………………………………………………
• ……………………………………………………………………
• …………………………………………………………………..
• ……………………………………………………………………….
2) Natural rubber
a) i) Name the polymer of rubber ( 1m)
………………………………………………………………………………………………………………..
ii) Draw the structural formula of natural rubber (1m)
………………………………………………………………………………………………………………………….
b) I) Name the rubber monomer (1m)
……………………………………………………………….
ii) draw structure of its monomer (1m)
……………………………………………………………………………………………………………
c) State 4 properties of natural rubber ( 4 m)

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I) …………………………………..
II) ……………………………………………………
III) ………………………………….……….
IV) …….……………………………….
d) DESCRIBE THE COAGULATION OF LATEX
Step 1 ( 7 m)
• Latex is a ……………………
• It consists of …………….… particles dispersed in ……………………..
• Each rubber particle is made-up many long-chain ……………..molecules
• enclosed by a ………………..…….-like membrane
• which is …………………… -charged
• The repulsion between the ……………………...charged particles
• prevent the ……………………… particles from coming close to each other
Draw labeled diagram ( 2m)
STEP 2 ( 6m)

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• When an ………………… is added to latex, OR when latex is exposed to …… ,
• the ………………..from the air enters the latex and
• produce ……………………….. acid that
• form ……………………………………………..…ions.
• This ………………………………...ions neutralize
• the ……………………………….. charges on the protein membrane.
Draw diagram ( 2m)
STEP 3 ( 3m)
• The rubber ……………………………………. can now come close together.
• This enable them to ……………………………….. with one another
• resulting in the ………………………………. of the protein membranes.
Draw diagram ( 3m)
STEP 4 ( 3m)
• The rubber molecules …………………………….… with one another

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• and get ……………………………... and
• thus causing latex to …………………………………………….
Draw diagram ( 2m)
e) Describe how to prevent the coagulation of latex ( 5m)
• By adding …………………………………..….solution,
• that contains ………………………………………..ions
• which ……………………………………………. the HYDROGEN IONS
• produced by the ………………………………………
• Therefore rubber particles remain …………………………… charged
f) In industry, how does the vulcanization of rubber is carried out? ( 4 marks)
By ………………………… latex with ……………………… or a …………………………………………………. in
……………………………………… as solvent
g) Describe how sulphur atoms change the properties of rubber in vulcanization

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( 4m)
 …………….….atoms form ……………….between rubber molecules
 These ………….…………………..
 prevent rubber ………………….. from sliding too much when ………………..
 The rubber molecules return to their …………………….... position after being stretched.
h) Draw cross-linkage of sulphur ( 2marks)
i) State 5 differences between vulcanized and unvulcanised ( 5marks)
Vulcanised Differences Unvulcanised rubber
End…..
1) a) What is the difference between a fat molecule and a fatty acid molecule? ( 4 marks)
• A fat molecule is formed when long-chained carboxylic acid

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• reacts with alcohol with (glycerol)
• A fatty acid molecule is carboxylic acid molecule
• that has a long chain carbon atom ( about 10- 20 atoms)
b) Fill in the table below to list differences between oils and fats.( 6 marks)
Oils Fats
Mostly unsaturated fat Saturated fats
d) sources Plants and animals Animals
e) Physical state at room liquid solid
temperature
f) Melting point Lower than 20 o C Higher than 20 o C
c) Explain how unsaturated fats can be changed to saturated fats? ( 6 marks)
• The hydrogenation process is carried out
• by bubbling hydrogen gas
• through hot liquid oil
• in the presence of fine particles of nickel catalyst
• at temperature of 200 o C and
• pressure 4 atm
2) Natural rubber
a) i) Name the polymer of rubber ( 1m)
Polyisoprene or poly-2-methylbut-1,3- diene

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ii) Draw the structural formula of natural rubber (1m)
b) I) Name the rubber monomer
isoprene or 2-methylbut-1,3- diene
ii) draw structure of its monomer!
c) State 4 properties of natural rubber ( 4 m)
V) WHITE SOLID AT ROOM TEMPERATURE ………………..1M

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VI) ELASTICITY THAT DECREASE OVERTIME …………………1M
VII) SOFT …………….1M
VIII) SENSITIVE TO HEAT……………………………….1M
d) DESCRIBE THE COAGULATION OF LATEX
Step 1 ( 7 m)
• Latex is a …………COLLOID…………
• It consists of ……RUBBER particles dispersed in ……WATER…
• Each rubber particle is made-up many long-chain ………RUBBER………..molecules
• enclosed by a ………PROTEIN..-like membrane
• which is ……NEGATIVELY-charged
• The repulsion between the ……NEGATIVELY …..charged particles
• prevent the ……RUBBER particles from coming close to each other
Draw diagram ( 2m)

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STEP 2 ( 6m)
• When an ACID is added to latex, OR when latex is exposed to AIR ,
• the BACTERIA ..from the air enters the latex and
• produce LACTIC acid that
• form HYDROGEN …ions.
• This HYDROGEN ….ions neutralize
• the NEGATIVE charges on the protein membrane.
Draw diagram ( 2m)

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STEP 3 ( 3m)
• The rubber PARTICLES can now come close together.
• This enable them to COLLIDE with one another
• resulting in the BREAKAGE of the protein membranes.
Draw diagram ( 3m)
STEP 4 ( 3m)
• The rubber molecules COMBINE …… with one another
• and get ENTANGLED .. and
• thus causing latex to COAGULATE
Draw diagram ( 2m)

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e) Describe how to prevent the coagulation of latex ( 5m)
• By adding AMMONIA ….solution,
• that contains …HYDROXIDE ……….ions
• which …NEUTRALIZE ………. the ( HYDROGEN IONS)
• produced by the bacteria .
• Therefore rubber particles remain …NEGATIVELY…… charged
f) In industry, how does the vulcanization of rubber is carried out? ( 4 marks)
By heating latex with SULPHUR or a solution of sulphur monochloride in
methylbenzene as solvent
g) Describe how sulphur atoms change the properties of rubber in vulcanization
( 4m)
 sulphur ….atoms form cross-link …between rubber molecules …………1m
 These cross – LINK …………………….. 1m
 prevent rubber MOLECULES from sliding too much when STRETCHED …1m
 The rubber molecules return to their ORIGINAL ….. position after being
stretched. ………………………1m

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h) Draw cross-linkage of sulphur ( 2marks)
i) State 5 differences between vulcanized and unvulcanised ( 5marks)
Vulcanised Differences Unvulcanised
rubber
More elastic Elasticity LESS elastic
Harder Hardness SOFTER
More tensile strength Tensile strength LESS tensile

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( the ability to hold load) strength
More resistance to heat Resistance to LESS resistance to
heat heat
LESS SOLUBLE Effect of organic MORE SOLUBLE
solvents