REQUIRED PRACTICAL 6: photosynthesis

Question 1

what is the first step

Answer 1

start be taking a boiling tube and placing it 10 cm away from an LED light source

Question 2

why is an LED light used ?

Answer 2

do not release very much heat

Question 3

why is too much heat not good

Answer 3

too much heat would change the temperature of the experiment

Question 4

what is the second step?

after taking a boiling tube and placing it 10cm away from an LED light

Answer 4

fill the boiling tube with sodium hydrogen carbonate solution

Question 5

why do we use sodium hydrocarbonate solution for the experiment

Answer 5

it releases carbon dioxide which is needed for photosynthesis

Question 6

what is the third step ?

after filling the tube with sodium hydrocarbonate solution

Answer 6

put a piece of pondweed into the boiling tube with the cut end at the top
and leave for 5 minutes
bubbles of oxygen gas should start appearing

Question 7

why do we leave the pondweed with the solution for 5 minutes?

Answer 7

to acclimatise to the conditions in the boiling tube

Question 8

what should we be able to see from the cut end of the pondweed?

Answer 8

bubbles of oxygen gas

that is produced by photosynthesis

Question 9

when seeing bubbles of oxygen gas being released by the cut end of the pond weed, where did this oxygen gas come from

Answer 9

it was produced by photosynthesis

Question 10

what is the fourth step after bubbles of gas appeared?

Answer 10

start a stop watch and count the number of bubbles produced in one minute, repeat this two more time (3x total) and calculate the mean number of bubbles produced in one minute

Question 11

what is the 5th step?

the step after starting a stopwatch and counting the numbers of bubbles produced in one minute, three times?

Answer 11

repeat this whole experiment agin from the start at 20cm from the LED, then 30cm then 40cm

Question 12

what are the problems with this experiment

what are the solution to these problems

Answer 12

problems:
the number of bubbles might be too fast to count accurately

the bubbles aren’t always the same size. A large bubble would count the same as a small bubble

solutions:
Measuring the volume of oxygen produced by a different practical experiment.

Question 13

how do we measure the volume of oxygen produced?

practical

Answer 13

• place the pondweed under a funnel and catch the bubbles in a measuring cylinder.
• use the measuring cylinder to measure the volume of the oxygen gas produced.

Question 14

describe the steps on how to measure the rate of photosynthesis under a lamp

Answer 14

• take a boiling tube and place 10cm away from an LED light
• fill tube with sodium hydrocarbonate solution
• place a pondweed with a cut end and leave for 5mins, bubbles should start appearing
• set a stopwatch for 1minute and count the bubbles produced in the one minute, do this another two times
• repeat whole experiment from 20cm away from lamp then 30cm then 40cm