Photosynthesis is the most important biological process on earth. Without it, we wouldn’t have air to breath or food to eat.
Investigating photosynthesis in the classroom poses its own challenges because the process can be difficult to observe. We’ve compiled here several experiments you can recreate in the classroom using easily accessible items to investigate how photosynthesis works.
Plants use energy from the sun to convert 6 carbon dioxide (CO2) molecules and 6 water molecules (H2O) into one glucose structure (C6H12O6) and 6 oxygen molecules (O2). This activity involves using lollies as atoms and toothpicks as bonds to make the molecules before photosynthesis and after photosynthesis.
Students will notice the same atoms are used for both equations. Lollies we used were red raspberries for oxygen, liquorice for the carbon atoms and mini white marshmallows for the hydrogen atoms.
Print this double sided page for an activity that’s ready to go.
In answer to the question at the bottom of the page, once the glucose molecule is absorbed by the body, 1 glucose molecule and 6 oxygen molecules will revert back to the pre-photosynthesis molecules, of 6 carbon dioxide molecules and 6 water molecules.
Leaf Disk Investigation
Leaves will naturally float because there are small pockets of air in it. If you force the air out using a vacuum (a syringe), and replace the air with solution (water mixed with sodium bicarbonate and a small amount of dish washing detergent), the rate of photosynthesis can be measured when the disks start to float again, as the oxygen produced through photosynthesis displaces the solution.
This experiment can be recreated in the classroom using this protocol.
The video below, by Paul Andersen is available at http://www.bozemanscience.com and is an excellent guide for this experiment.
Algae Balls Investigation
In this experiment, single celled algae are grown into a concentrated culture. The concentrated algae are then immobilised in a jelly-like substance, creating equal amounts of photosynthetic material in each sphere. Using a pH indicator, we can measure the rate of photosynthesis and the effect of variable contributing factors.
The experiment can be recreated in the classroom using this protocol created by the University of Reading. This activity was adapted from a resource developed through the Science and Plants for Schools (SAPS) programme. The original resource and others supporting biology education can be downloaded for free from the SAPS website: www.saps.org.uk
Leaf Pigment Chromatography
You can separate the two main chlorophyll pigments using the technique shown below by Alex Dainis (https://www.youtube.com/watch?v=qH-AJDqsSII). There are two main types of chlorophyll in leaves: chlorophyll A, which is bluish-green, and chlorophyll B, which is yellowish-green.
Or explore this video, by bludoorlabsmedia (https://www.youtube.com/watch?v=3N1Rt6nWczY)