# Aqa alevel Biology paper help !!

#1
A student used a Potometer to measure the movement of water through the shoot of a plant. As water is lost from the shoot, it is replaced by water from the capillary tube

1 . In one experiment, the air bubble moved 7.5mm in 15 minutes. The diameter of the capillary tube was 1.0mm
Calculate the rate of water uptake by the shoot in this experiment

Does rate if water uptake = distance traveled by the air bubble x area of cross section of capillary tube ???

I got 23.56, is that right ???

2 . The student wanted to determine the rate of water loss per mm^2 of surface area of the leaves of the shoot in the Potometer.
Outline a method she could have used to find this rate. You should assume that all water loss from the shoot is from the leaves

I have no idea how to answer this, any help would be great

3. The rate of water movement through a shoot in a Potometer may not be the same as the rate of water movement through the shoot of a whole plant
Suggest one reason why

Also don’t know what to do for this one

Any help would be awesome x
0
4 years ago
#2
Q1.

You mention an answer with NO UNITS - it means nothing, although the principle you suggest is correct!

7.5 mm in 15 min is = 7.5 X 4 mm movement in 1 hr = 30 mm/hr

Volume of liquid movement = pi X r^2 X h
= 3.14 X (0.5)^2 X 30
= 23.55 mm^3/hr

YES your answer is right (BUT Don't FORGET units - you will lose half of the marks!)

Q2 Adapt an experiment that you did with your teacher to achieve what the Q asks (should only need small changes)

Q3 Think of the "fair test" idea they teach you these days - What might be different between a few leaves in a potometer and a whole plant?
a) Shading of some leaves by others in a whole plant might reduce water loss
b) Stagnation of water vapour between leaves in a whole plant might mean less lost by transpiration per leaf.

Hope I have got you running - just do that final sprint for the tape and you have won the race!

M
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