1. Investigations with immobilised algae Paul Beaumont/Jenny Edrich
Science & Plants for Schools
Homerton College, Cambridge

2. A novel approach to photosynthesis practicals
Background
Debbie Eldridge
A novel approach to photosynthesis practicals
School Sci. Rev. (2004), 85,

3. Photosynthesis - problems
understanding experimental procedures
controlled experiments with conditions or materials missing followed by iodine test for starch.
with motivation
pupils have ‘done it before’ or see plants as tedious.

4. Photosynthesis - problems
obtaining data
difficulty getting enough reliable data to illustrate change in rates
Elodea bubbling rates notoriously unreliable.
keeping a range of photosynthetic organisms in school for use over the year.

5. New practical ideas Photosynthetic organisms easy to grow and culture.
The ability to be able to measure
either oxygen evolution
or carbon dioxide uptake so that rates can be determined.
A novel species.

6. Algae
Scenedesmus quadricauda

10. Enthusing the next generation
A report on the bioscience curriculum by a working group established by the
Biosciences Federation

12. Hydrogencarbonate indicator
Used to measure [CO2].
Orange/red in air.
Increasingly yellow as [CO2] increases .
Orange  red  magenta  deep purple as [CO2 ] decreases.

13. Hydrogencarbonate indicator
Buffers 7.6 –9.2

14. Light Sources
Buffers 7.6 –9.2

15. £30 each from:
Ring Lighting,
Ring House,
Gelderd Road,
Leeds LS12 6NB
Tel:

16. What might you observe?
The colorimeter we recommend for key stage 4 use is the WPA colorimeter

17. Dark control
60-90 min irradiation

18. Variables? Colour of light Light Intensity Number of balls Ball size
Distance from lamp
Neutral density experiment
Number of balls
Ball size
Concentration of algae
Temperature
The colorimeter we recommend for key stage 4 use is the WPA colorimeter

19. Colour of light
The colorimeter we recommend for key stage 4 use is the WPA colorimeter

20. 0%
100%
Red
Green
Blue

21. Light Intensity I
The colorimeter we recommend for key stage 4 use is the WPA colorimeter

22. Light Intensity II
The colorimeter we recommend for key stage 4 use is the WPA colorimeter

24. Transmission data Filter No Absorbance %T 298 0.15 71 209 0.30 50 210
0.60 25
211
0.90
12.5
299
1.20
6.25
The colorimeter we recommend for key stage 4 use is the WPA colorimeter

25. 100%
71%
50%
25%
12.5%
6.25%

26. Dark control
60-90 min irradiation

29. Filters LEE Filters – range of filters Different colours available
Neutral density options
LEE Filters, Central Way, Walworth Industrial Estate, Andover, Hants SP10 5AN.
Tel ;
The colorimeter we recommend for key stage 4 use is the WPA colorimeter

30. Can we quantify the colour change?
By measuring the absorbance using a colorimeter
By comparing the colours to a range of prepared buffer solutions.
The colorimeter we recommend for key stage 4 use is the WPA colorimeter

31. Colorimeter
Direction
of Beam
R = Reference T = Test

32. Hydrogencarbonate indicator
No access to a colorimeter?
Buffers 7.6 –9.2