Materials (per group):
- 4-5 Fresh Spinach Leaves
- Hole punch
- Plastic Syringe (or baby medicine syringe) needs to be blunt ended
- Forceps
- \( 2 \times 10 \mathrm{ml} \) measuring cylinder
- \( 500 \mathrm{ml} \) Beaker
- Liquid Soap (1 drop)
- Baking Soda (Sodium Bicarbonate): \( 1 / 8 \) teaspoon
- Stopwatch
- Glass rod
Method
To make Bicarbonate Solution:
1. Add \( 300 \mathrm{ml} \) distilled water to the beaker.
2. Add 1 drop of the liquid soap.
3. Add \( 1 / 8 \) of a teaspoon of Sodium bicarbonate.
4. Stir gently with a glass rod so as to not cause bubbles.
To make the discs:
5. Cut out 20 miniature discs from the spinach leaves using the hole punch. Ensure that you avoid the stem areas and ensure that all discs are the same size and not damaged.
6. Pull the end out of the plunger and put the 20 discs into the barrel.
7. Three-quarters fill the syringe chamber with the bicarbonate solution.
8. Draw back on the plunger to create a vacuum in the syringe. You will need to hold your finger over the end of the syringe.
9. Hold the vacuum for 8 seconds and release. You will need to complete this procedure of vacuuming for 8 seconds for 4 times in total.
10. Putting pressure on the leaf discs can also help, pushing instead of pulling the plunger.
11. All of the disks should now be sinking on the bottom. If not you can try shaking the syringe and vacuuming again. Once the leaves have all sunk to the bottom, try to keep them out of the light.
The Experiment:
12. Label 2 measuring cylinders ' \( A \) ' and ' \( B \) '.
13. Pour the discs (and solution) into the two \( 10 \mathrm{ml} \) measuring cylinders, so that you have exactly 10 discs in each measuring cylinder.
14. You may need to carefully use the forceps to move the leaf discs if need be.
15. Store measuring cylinder ' \( A \) ' in the cupboard - away from sunlight.
16. Store measuring cylinder ' \( B \) ' in direct sunlight. - either outside or on a window ledge. Ensure that it is somewhere safe and not going to be knocked over.
17. Start the stopwatch immediately.
18. Record the number of discs that have risen to the top at the end of each minute.
19. Record your results over a 12 minute period.
20. During the experiment, record any observations relating to the leaf discs that you may see.
