7. Study of water samples collected from different water bodies for their
pH, clarity and presence of living organisms (microscopic/ planktonic) observation
Answers
Answer:
Required Materials and Apparatus
Tile.
Tape.
Pins.
Beaker.
Needles.
Dropper.
Test tube.
pH paper.
Glass slides.
Cover slips.
Filter paper.
Secchi’s Disk.
Compound microscope.
Universal Indicator solution.
Procedure
To study pH levels:
Take two clean and dried test tubes.
Add the collected two different water samples into the two test tubes.
For a safer side, label the test tubes as A and B.
Dip the individual pH paper strips into the two different water samples.
Keep the strips on the tile and wait for the strips to dry.
Alternatively, pH levels of the water sample can also be found using the universal indicator solution.
Now, with the help of a dropper, add five drops of universal Indicator solution into both the test tubes.
Observe the change in colour in both the test tubes and compare the same with the colour chart.
Observation
Note the change in colour and associate the same with a broad range indicator paper to get a rough idea of the pH level.
To study the clarity of the water sample:
From a scientific perspective, the number of particles present in a liquid may make it cloudy or hazy. This property is called turbidity. The procedure for finding turbidity of a water body is as follows:
Reach the centre of a pond in a boat.
Immerse Secchi’s disc into the water, lowering it eventually until the black and white segments are no longer visible.
Mark the length on the rope, where the disk is not visible with a pin.
Name this position as “A”.
Carefully, bring the disc back up and mark the length of rope where the disc becomes visible again.
Name this position as “B”.
Use a meter tape to measure the length of section A to B.
Next, find the mean length of the rope by using X= (A+B)/2.
Answer:
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