March At-Home STEAM Activity: How Do Plants Breathe?

Explore how plants and trees breathe with this easy leaf science experiment and cool outdoor STEAM activity to help kids learn about photosynthesis and respiration. You are going to create an environment where you can actually SEE photosynthesis taking place – the oxygen/carbon dioxide process of plants! 

This activity is very interesting for two reasons:

First, kids don’t always think of plants and trees as ‘living’ things, so this helps them to visualize that concept.

Second, it’s a way to actually see something that is normally invisible! 

In this experiment, you will use a tree leaf or a leaf from a plant – the important step is using an active leaf (meaning one that you remove from a living tree or plant with stem intact). 


  • Large glass bowl
  • Warm water to fill the bowl
  • 1 large leaf from an outdoor tree or house plant
  • 1 small rock 
  • Magnifying glass (optional) 


  1. Fill the bowl with warm water.
  2. Place the leaf in the bowl.
  3. Gently submerge the leaf and place the rock on the leaf to keep it submerged. 
  4. Place the bowl in a sunny spot outside. 
  5. This is the most important step. WAIT. Time to put your science patience skills to the test.
  6. Check back in a few hours. You should be seeing small bubbles that form around the leaf and the edges of the bowl. These are easy to see with the naked eye or a magnifying glass. 

The Science Behind the Fun

Ask your little learners what would happen if they held their breath, went underwater in the pool and then let their breath out – they would see bubbles coming up in the water. 

That’s what they are seeing here – the leaf is using the sunlight as part of the photosynthesis process (where leaves convert sunlight to energy).

As a leaf creates that energy, it needs to get rid of the items it no longer needs so it will expel both the extra oxygen during photosynthesis along with water (the release of water from a plant is called transpiration). 

The process of photosynthesis is what allows us to see the bubbles – as the leaf releases its’ extra oxygen while submerged, the oxygen can be seen as bubbles in the water. And since oxygen is lighter than water, the bubbles will eventually rise to the surface.