Photosynthesis Required Practical
Method Problems with this method
1) Add sodium hydrocarbonate to a Bubbles can be too fast to count accurately
test tube of water
The bubbles may be different sizes – when
2) Place pondweed in it and cut it you’re counting them you count each bubble
underwater as one, and don’t consider the different sizes
3) Place in front of a lamp at 10cm which is difficult to do anyway.
4) Allow 5 minutes for it to To resolve this problem, measure the volume
acclimatise with a measuring cylinder and a funnel.
5) Set a stopwatch and count the
number of bubbles produced in Sodium hydrocarbonate is added to produce
ONE minute carbon dioxide which the plant needs
6) Repeat two more times then
The plant may be cut underwater to stop air
calculate the mean bubbles getting in
7) Then change the distance by
An LED light must be used or if a normal lamp is
10cm and do it again
used, a beaker of water must be placed in front
to absorb its heat. This is because temperature
affects the rate of photosynthesis.
Variables
Independent variable is the distance from lamp
Dependent variable is the amount of oxygen produced in one minute
Control variables include the temperature, concentration of sodium
hydrogencarbonate
Light intensity is directly proportional to
1
Distance squared
Method Problems with this method
1) Add sodium hydrocarbonate to a Bubbles can be too fast to count accurately
test tube of water
The bubbles may be different sizes – when
2) Place pondweed in it and cut it you’re counting them you count each bubble
underwater as one, and don’t consider the different sizes
3) Place in front of a lamp at 10cm which is difficult to do anyway.
4) Allow 5 minutes for it to To resolve this problem, measure the volume
acclimatise with a measuring cylinder and a funnel.
5) Set a stopwatch and count the
number of bubbles produced in Sodium hydrocarbonate is added to produce
ONE minute carbon dioxide which the plant needs
6) Repeat two more times then
The plant may be cut underwater to stop air
calculate the mean bubbles getting in
7) Then change the distance by
An LED light must be used or if a normal lamp is
10cm and do it again
used, a beaker of water must be placed in front
to absorb its heat. This is because temperature
affects the rate of photosynthesis.
Variables
Independent variable is the distance from lamp
Dependent variable is the amount of oxygen produced in one minute
Control variables include the temperature, concentration of sodium
hydrogencarbonate
Light intensity is directly proportional to
1
Distance squared
