exp 2.8 investigate the influence of light intensity on the rate of photosynthesis

Question 1

what is a suitable underwater plant for this experiement

Answer 1

fresh elodea

Question 2

why do we use an underwater plant?

Answer 2

so we can see oxygen bubbles in the water

Question 3

Method

Answer 3

cut the stem of the elodea
hook a paper clip onto the end of the elodea + drop it stem up into the boiling tube of pond water
place boiling tube into a water bath at 25 degrees
switch on light source and place the water bath containing elodea away from lamp and wait 5 min
observe bubbles being released. count and record the number of bubbles released per minute
repeat varying the distance of the lamp and the plant

Question 4

why do we hook a paper clip onto the elodea

Answer 4

holds the plant at the bottom of the boiling tube so we can see the bubbles rise up

Question 5

how do we ensure maximun concentration of Co2 in the water

Answer 5

1% w/v sodium hydrogen carbonate is in water

Question 6

what is the constant in this experiment

Answer 6

CO2

Question 7

what is the variable in this exp

Answer 7

light intensity

Question 8

why do we wait 5 min after adjusting the light intensity

Answer 8

allows the plant to adjust to the new light intensity

Question 9

why does the water bath have to be at 25 degrees

Answer 9

dark stage requires enzymes and this is the optimum temperature for enzyme activity

Question 10

how do we measure the rate of photosynthesis

Answer 10

bubbles produced per minute

more bubbles=more photosynthesis

Question 11

what is the formula for the light intensity

Answer 11

1 divided by distance in cm

Question 12

draw the graph

Answer 12

y axis= rate of photosynthesis
x axis = light intensity
L shape on its side kinda

Question 13

explain the graph

Answer 13

as light intensity increases, the plant absorbs more light and the rate of photosynthesis increases
the plant becomes light saturated ie it cannot absorb more light and the rate remains the same