Chemistry Paper 3 130514

1. An experiment experiment was carri carried ed out to compare compare the elastic elasticity ity of vulcanize vulcanized d and unvulcanized 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

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.#

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. ,3 mar-s

)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.

,3 mar-s )c* Based on the table constructed in )b*0 )i*

tate the method to manipulate the variable.

&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&. )ii*

tate what to record in the responding variable.

&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&.. &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&.. )iii*

tate how to maintain the controlled variable.

&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&.. &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&.. ,3 mar-s )d* tate the hypothesis for this experiment. &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& ,3 mar-s )e* 2f this experiment is continued by increase the mass of weight0 the rubber strip will snap. redict which rubber will snap first and state the type of rubber strips A and B. &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& ,3 mar-s

#. 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 agaragar 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

)a* Based on the observations0 complete the inferences in the table above. ,3 mar-s )b* 'rite halfe8uation in oxidation and reduction for rusting of iron. 9xidation : &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& (eduction : &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& ,3 mar-s )c* tate the operation definition for the rusting of iron. &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& ,3 mar-s )d* 4xplain why rusting of iron is the redox reaction. &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& ,3 mar-s )e* Based on this experiment classify the metals can provide sacrificial protection and metals that cannot provide sacrificial protection to iron. &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& ,3 mar-s )f* tate three ways to control rusting of iron. &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& &&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&& ,3 mar-s

3.

When sodium thiosulphate solution, Na 2S2O3 reacts 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*
 END OF THE QUESTIONS PAPER