Photosynthesis Experiments
Starch tests and oxygen counts show photosynthesis.
About this topic
Several classic experiments investigate photosynthesis. Starch testing with iodine on a destarched leaf shows starch only in the green, illuminated parts, proving light and chlorophyll are needed; a leaf in a flask with soda lime (absorbing CO₂) shows CO₂ is needed. Counting oxygen bubbles from pondweed at different light distances measures the rate.
Variegated leaves and covering part of the leaf with foil are controls. Boil the leaf in water and then alcohol first to remove chlorophyll so the colour change is visible.
To test for starch, destarch a plant by keeping it in the dark for 48 hours, expose part of a leaf to light, then boil the leaf in water, soak it in hot ethanol to remove chlorophyll, and add iodine; blue-black shows starch. Using a leaf with a white edge (variegated) proves chlorophyll is needed, and covering part with foil proves light is needed. Soda lime removes carbon dioxide to show it is needed.
Always take care: ethanol is flammable so use a water bath, not a flame. Controls are essential, for example a leaf in the dark with all other conditions the same. Pondweed under a funnel can be used to collect and test oxygen with a glowing splint, which relights. Students often forget the steps for removing chlorophyll, which would hide the colour change, or misread the result as the plant lacking starch.
Key ideas
- Iodine turns blue-black with starch
- Pondweed bubbles show oxygen
- Control variables
Quick check
Use cases: where Photosynthesis Experiments helps
- Homework: review the key idea behind Photosynthesis Experiments before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Photosynthesis Experiments without notes.
- Visual learning: play with the interactive lab to see how Photosynthesis Experiments changes when you adjust its inputs.
- Teaching a friend: explain Photosynthesis Experiments in your own words, then compare your version with the key ideas.
Biology underpins medicine, farming, conservation and biotechnology.
Frequently asked questions
What is Photosynthesis Experiments?
Starch tests and oxygen counts show photosynthesis.
What will I learn in Photosynthesis Experiments?
Iodine turns blue-black with starch. Pondweed bubbles show oxygen. Control variables.
Is Photosynthesis Experiments part of Biology?
Yes. It is one of 150 Biology topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the Photosynthesis Experiments lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study Photosynthesis Experiments?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.