Biology · Interactive
Photosynthesis
How plants use light energy to make their own food. Explore the equation, run the pondweed experiment, then test yourself.
The equation
Plants turn carbon dioxide and water into glucose and oxygen. Tap each part.
| Atom | Reactants | Products | Match |
|---|---|---|---|
| Carbon (C) | 66 × CO2 | 6from C6H12O6 | ✓ |
| Hydrogen (H) | 126 × H2O = 6 × 2 | 12from C6H12O6 | ✓ |
| Oxygen (O) | 18(6 × 2) + 6 = 12 + 6 | 186 + (6 × 2) = 6 + 12 | ✓ |
The atoms are rearranged, not created or destroyed. Light energy and chlorophyll are written by the arrow because they're needed, but they aren't atoms that end up in the products.
🧪 Pondweed experiment
Pondweed gives off bubbles of oxygen as it photosynthesises. Count the bubbles to measure the rate. Change one thing at a time, record your results and look for the pattern.
Closer lamp = more light. Doubling the distance gives about a quarter of the light.
Adding sodium hydrogen carbonate (NaHCO₃) to the water releases extra carbon dioxide.
Your results
How the ingredients get there
Tap part of the plant.
⚠️ Plants don't eat soil
Plants make their own food. Most of a plant's mass is made from carbon dioxide from the air, built into glucose by photosynthesis, plus water.
Soil supplies water and small amounts of mineral ions, like nitrates, that plants need to stay healthy and grow.
💡 Did you know?
What happens to the glucose?
Plants use the glucose they make in lots of different ways.
Quick check
Seven questions. You'll see why after each answer.