This activity page will offer:
Experience with acid/base indicators
to germinate seedlings
to observe the effects of biological processes on closed systems
shallow plastic containers with lids (from deli-section of grocery
container caps (from plastic soda container)
*This indicator solution is often sold in pet stores as a testing
tool for aquarium acidity levels.
As seeds germinate, they use oxygen to
breakdown molecules of sugar. This reaction (respiration) releases
the energy needed for the seeds to wake from dormancy. As sugar
is metabolized, Carbon Dioxide and water vapor are released. In
this activity, you will observe how respiration affects the gas
composition of a closed system. As seeds become metabolocally active,
the released Carbon Dioxide diffuses into an indicator dye solution.
The dye responds with a radical change in color.
- Work in groups of two. Clean and dry two shallow plastic containers
and airtight lids. Label one container "Bromthymol blue"
and the other "Non-
- Place a length of fluffed cotton along the inner margin of each
- Insert a variety of seeds into the space between the cotton
and each containers' wall.
- In the center of each container, place a small bottle cap. Position
the cap so that its well faces upwards.
- Use a medicine dropper to fill each cap with water
- Add several drops of bromthymol blue to the water-filled caps.
- Use the medicine dropper to dampen the cotton in one of the
containers. Keep the cotton within the other container dry.
- Seal both containers and place them side-by-side in a location
that is out of direct sunlight.
- Each day, observe the color of the indicator solution. Also
compare the appearance of the seeds.
- As the seeds germinate, observe and record any changes in the
- What was the role of the bromthymol indicator?
- Why was water added to the cotton?
- Why was the cotton in only one container dampened?
- Describe any changes in appearance of the indicator solution.
What can you infer from your observations?
Greening of Inquiry
that you are familiar with the action of bromthymol blue, it's your
turn to create a strategy for inquiry that would explore the effects
of photosynthesis within a closed air system. With access to the
same materials and small green plants, design a controlled experiment
that shows how photosynthesis affects the composition of the air
trapped within a sealed container.
An Historic Connection
In the eighteenth century, the English chemist, John Priestly, explored
the metabolic needs of living things. In doing so, he uncovered
the intimate relationship between plants and animals. When a healthy
mouse was placed in a sealed chamber, the animal showed signs of
distress caused by breathing "spoiled air". However, when a green
plant was placed into the sealed container with the mouse, the air
seemed to be purified. How can you explain these observations in
terms of the products of respiration and photosynthesis?
Dioxide, the Atmosphere, and Song Lyrics
It's time to write the lyrics for a song. Work with a partner. Select
a familiar poem or song - or write an original one. Research the
effects of increased amounts of carbon dioxide on our atmosphere.
Identify the major sources of this gas. Find out what natural processes
(both chemical and biological) help to buffer any quick changes
in the atmosphere's composition. Communicate this information as
lyrics to a song or poem. Share your creation with others in a classroom
"Concert for the Earth".
A non-intimating primer on acid/base indicators.
This site offers an introduction to germination and seed dormancy.
This rich, online resource offers a weekly review of topics that
addresses a variety of issues related to Carbon Dioxide and climate
activities in this guide were contributed by Michael DiSpezio, a
Massachusetts-based science writer and author of "Critical Thinking
Puzzles" and "Awesome Experiments in Light & Sound" (Sterling Publishing
Academic Advisors for this Guide:
Corrine Lowen, Science Department, Wayland Public Schools, Wayland,
Suzanne Panico, Science Teacher Mentor, Cambridge Public Schools,
Anne E. Jones, Science Department, Wayland Middle School, Wayland,
Gary Pinkall, Middle School Science Teacher, Great Bend Public Schools,
Great Bend, KS