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1. An experiment was carried out to compare the elasticity of vulcanized and unvulcanized

rubber. A 15 g weights were hung on 5 cm of rubber strips A and B as shown in diagram

1.1. The length of each rubber strips were measured after the weight were removed. The

experiment was repeated using 3 g and !5 g of weights.

"iagram 1.# shows the length of rubber strip A before the weight were hung and after weight

were removed.

"iagram 1.3 shows the length of rubber strip B before the weight hung and after the weight was

removed.

Rubber strip A

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Before experiment.

$ength %&&&&&&..cm

After 15 g of weight

'as removed.

$ength % &&&&&&& cm

After 3 g of weight

'as removed.

$ength % &&&&&&..cm

After !5 g of weight

'as removed.

$ength % &&&&&&&.cm

"iagram 1.#

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Rubber strip B

Before experiment.

$ength %&&&&&..cm

After 15 g of

'eight was

(emoved.

$ength %&&&&&.cm

After 3 g of

'eight was

(emoved.

$ength %&&&&&cm

After !5 g of

'eight was

(emoved.

$ength %&&&&&cm

"iagram 1.3

)a* +easure the length of each rubber strip and record the reading in the space provided

in diagram 1.# and 1.3.

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)b* /onstruct a table to record the length of each rubber strip before the 15 g of weight

was hung and after all the weights were removed.

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)c* Based on the table constructed in )b*0

)i* tate the method to manipulate the variable.

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)ii* tate what to record in the responding variable.

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)iii* tate how to maintain the controlled variable.

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)d* tate the hypothesis for this experiment.

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)e* 2f this experiment is continued by increase the mass of weight0 the rubber strip willsnap. redict which rubber will snap first and state the type of rubber strips A and B.

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#. The diagram # below shows the set up apparatus of the experiment to investigate the

effect of the metal on rushing of iron0 when it is in contact with other metals. Three iron

nails coil with different metals are placed separately into three test tubes A0 B0 /0 the test

tube " as a control. 4ach of the test tubes is filled with a agaragar solution containing a

small amount of phenolphthalein and potassium hexacyanoferrate )222* solution. The

apparatus is set aside for one day.

"iagram #

Table below shows the result of the experiment is set aside after 1 day.

Test tube A B / "

2ntensity of blue

colour

6one 6one 7ery high $ow

in- colouration resent resent resent resent

2nference

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)a* Based on the observations0 complete the inferences in the table above.

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)b* 'rite halfe8uation in oxidation and reduction for rusting of iron.

9xidation :

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(eduction :

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)c* tate the operation definition for the rusting of iron.

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)d* 4xplain why rusting of iron is the redox reaction.

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)e* Based on this experiment classify the metals can provide sacrificial protection and metals

that cannot provide sacrificial protection to iron.

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)f* tate three ways to control rusting of iron.

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3.

When sodium thiosulphate solution, Na2S2O3reacts with dilute

sulphuric acid, a yellow precipitate of sulphur is formed. he

temperatures of sodium thiosulphate affect the rate of reaction.

(eferring to the above information0 design a laboratory experiment to investigate the

effect of the temperature of reactant on the rate of reaction.

;our planning must include the following items:

)a* tatement of the problem

)b* All the variables

)c*