How To Perform a Photosynthesis Experiment

Organisms need energy for survival. Light coming from the sun is being transformed into chemical energy in an organic material through the process of photosynthesis. Photosynthesis happens in plants and some forms of algae (those belonging in Kingdom Protista). It is indeed a very complex process that includes the utilization of heat coming from the sun in transforming water and carbon dioxide to produce glucose and oxygen gas. While humans are giving off carbon dioxide gases in the atmosphere, the plants are inhaling these gases and using it to produce their own food. Photosynthesis usually occurs at the chloroplasts. Chlorophyll is the green pigment primarily involved in this process. The process usually happens in the leaves of plants and very rarely in stems, etc.

How can you perform your own photosynthesis experiment activity? Here is an easy laboratory experiment that will explain how to understand the process more clearly. In this activity, you will use algae. It is a one-celled plant that is useful in the field of medicine, especially in general research (when it comes to gene engineering and diagnostics).


  • To be able to explain the importance of photosynthesis in the survival of human beings as well as other organisms.
  • To show high school students how algae works well with the photosynthetic process and how these organisms can be easily grown for experimental purposes.
  • To be able to understand how carbon dioxide is vital for photosynthesis.


  1. Grow your algae in a medium-sized test tube or Petri dish. Get a concentrated amount of algae from your medium. You can strain the liquid medium in which these organisms are growing to get a concentrated population.
  2. Set aside your algal preparation.
  3. In a medium-sized beaker, add about 3 ml of sodium alginate solution (jelly).
  4. Pour in 5ml of your algal cell concentration.
  5. Mix evenly with a stirring rod.
  6. Pour your green jelly-algal solution into an open ended syringe into a beaker with a solution of 2% CaCl.
  7. As your algal solution drops on your calcium chloride mixture, swirl your beaker gently to form tiny algae balls.
  8. Leave the set-up for around 10-20 minutes.
  9. Wash the algal balls that you have formed with distilled water. You may use a strainer to separate the solid particles.
  10. After making your algal balls, you may now use them in determining the rate of CO2 absorption. This will show how fast the photosynthetic process is occurring.
  11. Prepare several containers with lids on them and add in a small volume of the hydrocarbonate indicator to each container.
  12. Put in equal numbers of algal balls in each glass container.
  13. Place your containers at varying light intensities and leave the set-ups for about 1-3 hrs.
  14. Compare the color changes that you have on the different set-ups. A yellowish lighter color indicates an increasing CO2 concentration and a darker magenta color will indicate a decreasing CO2 concentration. You may also use a little bit of technology here, like a colorimeter, for more accurate results.

This is just one simple laboratory activity for photosynthesis. There are other interesting experiments that you can choose from. You may research on the Web or scroll over your high school science books.  


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