Core Practical - Light Intensity And Photosynthesis

Question 1

describe the method used to carry out this practical:

Answer 1

1-A lamp with an LED bulb is set up at different distances from the plant in a beaker of water:

2-sodium hydrogen carbonate (NaHCO3) is added to the water to supply the reactant carbon dioxide to the plant

Question 2

why is an LED bulb used?

Answer 2

an LED bulb is best as this will not raise the temperature of the water

Question 3

what will happen to light intensity as the lamp is moved further away?

Answer 3

the light intensity is proportional to distance - it will decrease as the distance away from the bulb increases.

Question 4

what is recorded during this experiment?

Answer 4

The bubbles produced since rate of photosynthesis is the number of bubbles produced per minute.

Question 5

what is the independent variable within this practical?

Answer 5

distance from the light source/light intensity

Question 6

what is the dependent variable within this practical?

Answer 6

the number of bubbles produced per minute

Question 7

what is the control variable within this practical? (3)

Answer 7

concentration of sodium hydrogen carbonate solution
temperature
using the same piece of pondweed each time

Question 8

what is a risk within this practical? (2)

Answer 8

Care must be taken when using water near electrical equipment.
Ensure that your hands are dry when handling the lamp.

Question 9

how could the volume of oxygen produced be collected?

what could we use to measure the changes in oxygen concentration in the water?

Answer 9

-by collecting the gas produced in a gas syringe.

-the changes in the oxygen concentration in the water could be measured using data logging equipment

Question 10

what is the rate of photosynthesis equal to?

Answer 10

the number of bubbles produced per minute