The Becker Bottle—“One in a Million Too”

Introduction

How big is a million? How long would it take to count to one million? How long would it take to measure out one million objects? Is there a shortcut for measuring out such large quantities? What does “part per million” mean? Can something that is present at a concentration of only one part per million have any real consequence? How can we measure concentrations that are as low as one part per million or even smaller?

Many science disciplines deal with questions like these. The science world is full of very large numbers. For example, how many planets are in the universe? How many miles away is that star? Consider the enormity of a mole. We want our science students to get an idea of how much a mole actually represents. To do this, let them consider that a million is to a mole (6 x 10²³) as ¼ teaspoon of water is to Lake Michigan! Scientists have to use scientific notation (e.g., 10²³) or special prefixes (e.g., kilo, mega) to discuss the huge numbers relative to science.

Equally difficult to comprehend are very small numbers (e.g., 10^–23). Some compounds in very small concentrations can have quite significant consequences to humans. For example, the EPA considers water unfit for human consumption if cadmium levels are above 10 ppb (0.00000001)! How can that be measured?

Concepts

• Background interference
• Molecular concentration
• Parts per million (ppm)

Background

The original Becker Bottle with its blue “solvent” background has proven to be a valuable teaching aid. It has been especially useful in making the concept of ppm become more concrete for students. The original Becker Bottle contains one million tiny colored spheres (actually decorative cake sprinkles, 2.5 kg of them!) The sprinkles are of different colors and are in concentrations of 100,000 ppm, 10,000 ppm, 1,000 ppm, 100 ppm, 10 ppm and 1 ppm (the one black sphere). Finding the black sphere is extremely difficult and really makes one million seem like the large number that it is.

The color arrangement in Becker Bottle Too raises new issues that conflict with the concepts of the original bottle. Will the mixture (1 black sphere in 999,999 yellow spheres) make the concept of 1 ppm appear different? Can our perception of a large number be changed? Will it be easier to find the black sphere? What effect does the “background” have on an object in real life? Does the total mixture make testing for a specific item harder or easier? Does the background (solvent) affect the rate of chemical reactions? Does it affect our ability to test accurately for a specific item? All of these questions and more are raised by the Becker Bottle Too.

Safety Precautions

The Becker Bottle has been sealed to prevent accidental spilling and contamination. Keep it sealed and do not allow any consumption of the sprinkles.

Teacher Tips

• After much use, the inside surface of the bottle may become slightly scuffed, diminishing the clarity of the plastic. Should this happen, you may simply transfer the sprinkles into a new 3-L bottle (rinsed out and allowed to dry thoroughly). If kept dry, the bottle can be used for many years.

Discussion

1. Be sure to complete all of the activities/discussions with the original Becker Bottle—“One in a Million” before revealing the Becker Bottle Too. See The Becker Bottle—“One in a Million” for activity ideas.
2. Have a race to find the black bead in both bottles. Divide the class and have a race. Which bottle is easiest? Why? Challenge students by pointing out that the concentration of the black bead is the same in both bottles—1 ppm! Ask questions like these to your students:
   • Is it easier to find 1 ppm in a homogenous solvent background with our eyes?
   • How about chemically? /li>
   • Does background affect chemical testing procedures? /li>
   • How do we see molecules? /li>
   • Does the background color matter?
3. Ask the students to consider the situation if the “black” sphere was the same color as the other spheres. What other properties or physical attributes might be used to identify the “one” black sphere. Some ideas might include size, mass, magnetic property, heat capacity, etc.
4. Discuss ways in which the Becker Bottle—“One in a Million Too” is an accurate simulation model. In what ways is this simulation not accurate?
5. Secure test kits that measure in ppm. Determine if the chemistry is affected by the “background.”

References

This bottle was created by Bob Becker, Kirkwood High School, Kirkwood, MO.