Photosynthesis Bubble Lab
Set up a virtual pondweed beaker, turn on the lamp, and count the oxygen bubbles that rise to the surface. Change the light, the distance to the lamp, the water temperature, and the carbon dioxide level to find out what makes photosynthesis go faster or slower.
Guided Experiment: How does light intensity affect photosynthesis?
If you give the pondweed more light, what do you predict will happen to the number of bubbles produced each minute?
Write your hypothesis in the Lab Report panel, then click Next.
Controls
Results
What the bubbles mean
Each bubble is oxygen gas released by the pondweed during photosynthesis. A higher bubble count means a faster reaction. If bubbles stop, photosynthesis has slowed or stopped because one of the conditions is no longer good enough.
Data Table
(0 rows)| # | Trial | Light(%) | Distance(cm) | Temperature(°C) | CO₂ | Bubbles/min |
|---|
Reference Guide
What is photosynthesis
Photosynthesis is how plants make food. Inside their leaves, plants take in water from their roots and carbon dioxide from the air. Sunlight gives them the energy to build sugar.
As the plant builds sugar, it also makes oxygen. Land plants release this oxygen through tiny holes in their leaves. Water plants like pondweed release it as bubbles that rise to the surface.
In short, photosynthesis turns light, water, and carbon dioxide into food and oxygen.
What affects the rate
The speed of photosynthesis depends on three main conditions.
- Light. More light gives the plant more energy, up to a point.
- Carbon dioxide. More CO₂ in the water gives the plant more raw material.
- Temperature. Plants work best at warm room temperatures. Too cold or too hot slows them down.
Whichever condition is in shortest supply is called the limiting factor. Improving the limiting factor speeds up the reaction the most.
The pondweed experiment
Real scientists run this experiment with a pondweed called elodea. They place a stem of pondweed in a beaker of water and shine a lamp on it. The pondweed gives off oxygen bubbles from the cut end.
To measure the rate, students count the bubbles for one minute. They change one condition at a time and keep the others the same. This is called a fair test.
In this lab the beaker, water, lamp, and pondweed are all simulated, so the bubble count comes out the same every time you use the same settings.
Why count bubbles
Each bubble is made of oxygen, one of the products of photosynthesis. If the plant is photosynthesising quickly, it makes more bubbles. If it slows down, the bubble count drops.
Counting bubbles is a simple way to measure the reaction without expensive equipment. It is not perfect, because bubbles can come in different sizes, but it is a fair way to compare conditions in a classroom or in this simulation.
When you read your results, look for trends. Does the bubble count keep climbing, or does it level off when one of the factors becomes the limiting factor?
