Correction
Biology PKBS 2
Form 5 - Paper 3 Qn 2 (BOD).
#{ 1 time= 1 BI, 5 times = 3 BI + 2 BM , 8 times = 5 BI + 3 BM, 10 times = 6 BI + 4 BM }#
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Sample answer:
1. Problem
Statement: What is the effect of different distance between the rubber factory
and the village on the rate of water pollution?
2. Aim : To investigate the effect of the distance between the rubber factory
and the villages on the rate of water pollution.
3.Hypothesis: The longer the distance between the rubber factory and the
villanges , the lower the rate of water pollution.
4. Variables:
Manipulated V: The distance between the rubber factory and the villages.
Responding V: The rate of water pollution // The time taken for the methylene
blue solution to decolourised.
Control V: The volume of the methylene blue solution
5. Apparatus
& Materials : water samples, methylene blue solution, reagent bottle,
stop-watch, syringe, cupboard
6Technique : Record the time taken for the methylene blue solution to turn colourless
7. PRocedure:
- Water samples are taken from the river at villages P, Q and R
- 200ml of water sample from village P is transfered into the reagent bottle P.
- Using a syringe, 1ml of 1% methylene blue solution is slowly injected
into the water sample P.
- The tip of the syringe is used to stir the solution slowly.
- The bottle is capped immediately and placed in a cupboard.
- The stop watch is started.
- The reagent bottle is observed every one hour to determine whether the
methylene blue has been decolourised.
- The time taken for the methylene blue to decolourised is taken and recorded down.
- Steps 2 to 8 are repeated with the sample water from villages Q and R.
- The results are recorded in a table.
Result:
Water sample. | Time taken for methylene blue solution to turn colourless (min) | The rate of water pollution 1/t (min-1) |
P | | |
Q | | |
R | | |
Consclution : The longer the distance between the rubber factory and the villanges
, the lower the rate of water pollution. The hypothesis is accepted.