Light intensity and photosynthesis core practical

Question 1

A

Answer 1

Decide on the different distances between the algae and the lamp you are going to use.

Question 2

B

Answer 2

For each distance you will need one clear glass bottle. You will also need one extra bottle.

Question 3

C

Answer 3

Add 20 of the algal balls to each bottle.

Question 4

D

Answer 4

Add the same amount of indicator solution to each bottle, and put on the bottle caps.

Question 5

E

Answer 5

Your teacher will have a range of bottles showing the colours of the indicator at different pHs. Compare the colour in your tubes with this pH range to work out the pH at the start.

Question 6

F

Answer 6

Set up a tank of water between the lamp and the area where you will place your tubes. Take extreme care not to spill water near electrical apparatus (such as a lamp).

Question 7

G

Answer 7

Cover one bottle in kitchen foil, so that it is in the dark.
H Measure the different distances from the lamp. Place your bottles at those distances. Put the bottle covered in kitchen foil next to the bottle that is closest to the lamp.

Question 8

I

Answer 8

Turn on the lamp and wait until you can see obvious changes in the colours in your bottles. The longer you can wait, the more obvious your results are likely to be.

Question 9

J

Answer 9

Compare the colours of all your bottles with the pH range bottles. Write down the pHs of the solutions in your bottles.

Question 10

K

Answer 10

For each bottle, calculate the ‘change in pH/hour’. L Plot a suitable graph or chart of your results.