Light Intensity On Photosynthesis

Question 1

What is the independent variable?

Answer 1

Light intensity
Distance between light and plant

Question 2

What is the dependent variable?

Answer 2

Rate of photosynthesis
Number of bubbles in a certain time

Question 3

What are some control variables?

Answer 3

Same mass of sodium hydrogen carbonate solution
Temperature
Plant species and size
Surroundings.
Time to acclimatise

Question 4

Write a method for this practical

Answer 4

1. Put your 10 cm piece of pond weed (cut edge at top) into a boiling tube and then a beaker of water.
2. Use the ruler to position the beaker of pondweed 1 metre away from the light source.
3. Start the stop watch and count and record the number of bubbles released in three minutes
4. Record your results in a table
5. Move the light source so that the pondweed beaker is 80 cm away.
   Then repeat steps 3 and 4.
6. Repeat for distances of 60, 40 and 20 cm

Question 5

Why is sodium hydrogen carbonate solution used instead of just water?

Answer 5

Sodium hydrogen carbonate solution is used to provide the pondweed with the carbon dioxide needed for photosynthesis.