What is photosynthesis? What are the necessary conditions for it? Don't just remember, let's do an experiment and learn.
Duration 40 Min
Difficulty 3/4

Material list

What is happening

Plants cook their food through photosynthesis, it requires water, carbon dioxide and light. If we provide al these photosynthesis starts and as a by-product oxygen is produced, and this oxygen is the reason for the leaf disc in the experiment to float.


Gather the materials

Baking soda and liquid soap can be purchased from a stationary shop and plastic syringe from a medical store.

Step 01

Fill two glasses with equal amount of water

Take two similar glasses or any transparent container and fill it with equal amounts of water.

Step 02

Add soap to the water

Add a few drops of liquid soap water in both glasses and mix.

Step 03

Add baking soda to one glass

Add a small spoon of baking soda to one of the glass. Mark it as ‘With baking soda‘.

Step 04

Cut leaf discs

Use the tip of a plastic straw to cut leaves into small discs. Gently press the straw by putting a leaf between your thumb and straw.

Step 05

Put leaf discs into syringe

Remove the piston of the syringe and put leaf discs into the barrel.

Step 06

Draw water into syringe

Draw a few mL of water into the syringe. The leaf disks should float in the water because of the air content in the leaves.

Step 07

Suck air out of the leaves

Hold the syringe as its tip on top and expel the air by slowly pushing on the piston. Close the tip of the syringe tightly with your finger. Create a slight vacuum by gently pulling the piston. Hold it for a few seconds, and then release it. Repeat 2-3 times till all leaf disks sink to the bottom.

Step 08

Transfer the solution into glasses

Transfer the leaf discs into the glasses, the discs will begin to settle at the bottom

Step 09

Place the glasses under a light source

Place the glasses under sunlight or any other light source. Notice tiny bubbles forming on the discs on glass-2. After a few minutes, the discs on the glass-2 will begin to float. No changes happened to glass-1, why?

Step 10

More Science

Plants cook their food through photosynthesis, it requires water, carbon dioxide and light. As a by-product oxygen is also produced. The Leaf discs in the experiment  extract water from the prepared solution. And baking soda (sodium bicarbonate) provides the required carbon dioxide. If a light source is present, photosynthesis begins. Plant material generally floats in water, it is due to the air content inside. If a gentle vacuum is applied, the air inside the leaf disks is forced out, causing it to sink. When  photosynthesis begins, oxygen bubbles are produced by the leaves, making them float again.

Extra bit: When all the disks are afloat, move the flask to a dark room, or cover the whole flask with a cloth. Check it after fifteen minutes. What happens to the disks?


Recent Updates

Make Blacklight

It's super easy to make a black light with your smartphone.

Hooey Stick

Hooey stick is a wooden toy that has probably amused children...

Impossible to Mix

You can shake this one all day long-it will always return...

Floating Leaves

What is photosynthesis? Don't just remember, let's do an experiment and...

Fire Foam

Let's do an experiment to generate hydrogen and make it blast!...