Science Experiment: Testing for Starch in Leaves
Our young scientists conducted an exciting experiment to discover how plants make their own food! 🌱🔍 Using a simple iodine test, we checked for the presence of starch in leaves—proof that photosynthesis is happening.
Plants produce their own food through the process of photosynthesis, where sunlight, carbon dioxide, and water are converted into glucose (sugar). Excess glucose is stored as starch in the leaves. This experiment helps children understand how plants make food and how we can test for the presence of starch using iodine solution.
Materials Used:
A fresh green leaf (from a plant exposed to sunlight)
A pot of boiling water
A beaker or small bowl
Ethanol (or rubbing alcohol)
Iodine solution (Lugol’s iodine or tincture of iodine)
Tweezers
White tile or petri dish
Safety goggles (for children observing)
Procedure:
Step 1: Selection of Leaf
A healthy green leaf was plucked from a plant that had been exposed to sunlight for several hours.
Step 2: Boiling the Leaf
The leaf was placed in boiling water for 2-3 minutes to soften it and break down cell membranes.
Step 3: Removing Chlorophyll
The leaf was then placed in a small beaker with ethanol (alcohol) and heated gently in a water bath.
The ethanol turned green as chlorophyll was extracted, leaving the leaf pale and brittle.
Step 4: Rinsing and Iodine Test
The leaf was rinsed in warm water to remove excess alcohol.
It was then placed on a white tile, and a few drops of iodine solution were added.
Observations:
The parts of the leaf that had been exposed to sunlight turned blue-black, indicating the presence of starch.
Areas that were covered (if tested with a variegated leaf) remained brownish-yellow, showing no starch.
Learning Outcomes for Children:
Understanding photosynthesis in a simple, hands-on way.
Observing chemical changes (color change with iodine).
Developing scientific curiosity and analytical skills.
Safety Note:
Adult supervision was maintained during boiling and use of alcohol/iodine.
Children observed the experiment while wearing safety goggles.
Conclusion:
The experiment confirmed that leaves produce starch through photosynthesis when exposed to sunlight. The iodine test is an effective way to detect starch, as iodine reacts with starch to form a dark blue-black color.
