PBS - Scientific American Frontiers | Beneath the Sea | Teaching Guide

Sunlight that penetrates the ocean is absorbed as it passes through the surface layers of the water. Since solar radiation does not reach the ocean depths, the bottom of the deep ocean remains largely in complete darkness. However, certain animals in this extreme environment can generate light to communicate with each other, and even to lure prey, thanks to a process known as bioluminescence.

Bioluminescence is a form of chemiluminescence - the production of light through chemical means. In contrast to light generated by high temperatures which allows objects to get hot (such as light bulbs, stars, or fireplace pokers), this "cool" process relies on chemical reactions. When chemicals combine, they release the energy that has been stored in their chemical bonds. In chemiluminescent reactions, this stored energy is released as light. In most bioluminescent deep sea animals two basic chemicals - luciferin and luciferase-combine to produce light as a by-product of the reaction.

You may also have seen chemiluminescent sticks, bracelets, or other items that depend upon chemical reactions to produce light. If you examine these items closely, you will find that they consist of a sealed vial immersed within another liquid. When the inner vial is crushed, its contents mixes with the surrounding fluid. As the chemicals combine, they generate visible light. In this activity, you'll explore how the temperature of the chemicals that combine affects a chemiluminescent reaction. targets.


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This activity page will offer:

Introduction to chemiluminescence and bioluminescence
Opportunity to observe the effect of temperature on reaction
Activity that integrates art and science

MATERIALS

Three chemiluminescent sticks (also called "cool light sticks")

Thermometer Beakers (large enough to submerge one stick)

Ice water

Warm water

Room-temperature water

Timer

Digital camera (optional)

NOTE: Cool light sticks are available at many toy stores, marine supply stores, party goods stores, and stores offering camping and fishing supplies.

PROCEDURE

Work in a team of three students. Identify a space in which the lights can be turned off and the shades drawn shut.

Fill one beaker with ice water. Fill another with room temperature water. Fill a third one with lukewarm water.

Insert a light stick in each of the water-filled beakers, but do not activate it. Try to immerse as much of the stick in the water bath as possible.
NOTE: You may have to tie a small weight onto the stick to insure that it does not float to the surface.

Wait several minutes. Then use a thermometer to measure the temperature of the water in each of the three beakers. Record these values.

Activate all three light sticks.

Shut the room lights. Compare and contrast the brightness of the generated light. Which beaker contains the brightest stick? Which beaker contains the dimmest stick? Record you observations.

If you have a digital camera, use it to capture a record of the light generated by these side-by-side tubes. Make sure that all three glowing sticks are included in the same single image. Once the image is taken, you can return the room lights to their normal level.

At 15-minute intervals, dim the room lights. Use the digital camera to capture additional images of the three glowing light sticks.

Continue comparing and contrast the relative brightness of the three sticks. If applicable, note the time at which each stick no longer appears to glow.

Questions

In step 3, why was it necessary to place the light sticks in the water-filled beakers for several minutes before performing the activity?

In step 6, why was it necessary to include all three sticks in the same image?

In which beaker did the stick glow brightest?

In which beaker did the stick glow dimmest?

In which beaker did the glow last longest?

In which beaker did the glow go away the quickest?

Is the brightness of the glow related to the time that this effect lasts? Explain.

The rate of a reaction is dependent upon several factors, including the temperature of the reaction vessel. How can this concept be applied to your observations?

EXTENSIONS

Glowing Artwork
Some animals have light organs that are concentrated around the eyes. Other organisms have strands of light spots that extend their whole body length. Check out this site to learn more about the placement patterns of light organs in fish, cephalopods, jellyfish and other organisms.

For this activity, you'll need both a set of standard watercolor paints and a small vial of glow-in-the-dark paint. You can obtain all of these non-toxic paints from a local art store or an Internet outlet. Use the standard paints to produce images of various deep-sea fish and invertebrates. Then, use the glowing paint to add a pattern of glowing spots to each drawing. Challenge students to identify the painted subjects by only the glowing patterns that are revealed in dimmed lighting.

WEB CONNECTION

The Ocean Depths
An overview of the deep ocean environment and the organisms that inhabit it.

Marine Bioluminescence
Scripts Institute of Technology presents a list of Internet sites that pertain to bioluminescence.

Fireflies-Illuminating a Brighter Future for Science
This site presents a small library of video clips captured by ROVs.

The 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 Co., NY).

Academic Advisors for this Guide:
Corrine Lowen, Science Department, Wayland Public Schools, Wayland, MA
Suzanne Panico, Science Teacher Mentor, Cambridge Public Schools, Cambridge, MA
Anne E. Jones, Science Department, Wayland Middle School, Wayland, MA