Botanical Leaf Stomata Evaporative Microclimate Chamber

45 mins Ages 10-14 Indoor

A challenging, hands-on discovery and STEM project designed for curious young minds aged 10 to 14.

Materials Needed

  • • Cobalt chloride humidity test strips (blue when dry) (2 strips)
  • • Fresh broad leaf (e.g., lilac, ficus, or geranium) (1 leaf)
  • • Glass microscope slides or clear rigid plastic covers (2 units)
  • • Clear tape and stopwatch (1 set)

Pro Tips

  • → Cobalt chloride paper is bright blue when completely dry, turning pink when exposed to water vapor.
  • → Tape a test strip against the top of a fresh leaf, and another against the bottom surface, sandwiching the leaf between two glass slides.
  • → The paper on the bottom surface turns pink within minutes, proving that the vast majority of stomata pores sit on the shaded underside.

Safety First

Cobalt chloride indicator paper is safe to handle dry; do not ingest or chew on test strips.

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Step-by-Step Instructions

1

Step 1

Cut two small squares of blue cobalt chloride humidity indicator paper.

2

Step 2

Pick a fresh, healthy broad leaf from a garden plant and immediately place one paper square on top and one on the bottom.

3

Step 3

Sandwich the leaf between two clear glass slides and tape the edges tightly to seal the testing chamber.

4

Step 4

Observe the paper strips: the bottom strip turns pink within 10 minutes, showing higher stomata density on the lower leaf surface.

What they are learning

Stomatal transpiration density comparison Cobalt chloride chemical humidity indication Leaf upper vs. lower surface moisture exchange