Air in a Bottle

Introduction

What is the composition of the Earth’s atmosphere? How can one teach a concept that cannot be seen? The Air in a Bottle model is an excellent teaching tool to show students a representation of the composition of the atmosphere and associated concentrations. In addition, this demonstration can specifically show concepts such as “how big is a million?” Students often have difficulty visualizing very large or very small numbers. Simplify these concepts for the students with this model!

Concepts

• Parts per million
• Molecular concentration
• Composition of Earth’s atmosphere

Background

The Air in a Bottle model represents the composition of the atmosphere in ppm by volume. Colors of the different particles at the listed concentrations (shown in Table 1) include: yellow, red, blue, white, green and black. Challenge your students to identify the gases making up air based on the colors in the bottle.

Safety Precautions

The Air in a Bottle model has been sealed to prevent accidental spilling and contamination. Keep the bottle sealed and do not allow any consumption of the food-grade particles making up the model.

Procedure

1. Hold the Air in a Bottle model in front of the class and ask the students to make observations.
2. Without telling the students the answers, discuss the concentrations of the different gases in air as they are represented in the bottle and instruct the students to identify the color of each gas. (Students may need helpful hints for color determination of smaller concentrations of gases as they may be difficult to find in the bottle.)
3. Pass the Air in a Bottle model around and have the students shake the bottle and consider the model more closely. Leading questions for students to consider include: What’s the lowest concentration you can easily identify.
4. After making observations, instruct the students to fill out the data table on the Air in a Bottle Worksheet and answer the questions.

Student Worksheet PDF

11999_Student1.pdf

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.
• As an extension to this demonstration, challenge students to determine the mass of air in the classroom. Contact Flinn Scientific and request Publication No. 10088 for instructions for this activity.

Sample Data

Answers to Questions

1. Look at the Air in Bottle model closely and fill out the table. Summarize your findings.

   The yellow colored particles represent nitrogen, which is the background in the Air in a Bottle model. The red (oxygen) have been mixed at a concentration of 200,000 ppm, the blue (argon) are present at 9,000 ppm, the white (carbon dioxide) are at 400 ppm, the green (neon) are at 18 ppm, and the black particles (helium, methane, krypton, and hydrogen combined) represent a total of 9 ppm.

2. How is the Air in a Bottle model similar to the Earth’s atmosphere? How is it different?

   The concentrations of the particles in the bottle are similar to the concentrations of the representative gases in the Earth’s atmosphere. The particles in the bottle have definite size and mass, as do the gas molecules that make up the air. The model is different in two important ways however. First, gas particles would be completely filling the space instead of remaining closely packed, as the solid particles are. Secondly, however, most of a container of gas is empty space as the particle density is very low.

3. The concentration of carbon dioxide is significantly smaller than oxygen and nitrogen in the air, yet it has such important environmental impacts. It is present at a concentration of 400 ppm in the atmosphere; did you find it in the Air in a Bottle model? What are the environmental impacts of carbon dioxide?

   Carbon dioxide is a greenhouse gas; it absorbs and emits infrared radiation. Accumulation in concentrations of greenhouse gases may lead to increased emission of infrared radiation. In addition, carbon dioxide combines with water to form carbonic acid and causes natural rain water to be slightly acidic.

CO₂ + H₂O → H₂CO₃

4. Imagine the Air in a Bottle model being a greater volume or lesser volume with the same amount of particles. What might this represent?

Gases may expand or be compressed, therefore imagining the air inside the bottle being a greater volume or lesser volume with the same amount of particles may represent differences in atmospheric pressure.

5. Convert the units of ppm of each gas into a percent.

Nitrogen 78% 
Oxygen 20% 
Argon 0.9% 
Carbon dioxide 0.04% 
Neon 0.0019%
Helium 0.0005%
Methane 0.0002%
Krypton 0.0001%
Hydrogen 0.0001%

Sample Calculation:

Discussion

The Air in a Bottle model may be integrated into numerous lessons and help simplify various “can’t see concepts” for many students. The Air in a Bottle model may also raise questions about environmental concepts, such as air pollution and air quality. For example, carbon dioxide is usually present at low concentrations (e.g., 0.04%) of total air, yet it greatly impacts the environment. The Air in a Bottle model idea was adapted from The Flinn Scientific Becker Bottle One in a Million and The Becker Bottle One in a Million Too products. The Air in a Bottle is an excellent addition to this family of models because it designates a compound to its respective ppm concentration. The model consists of a 3-L bottle and one million tiny colored spheres—2.5 kg of decorative cake sprinkles!

References

Special thanks to Scott Newkirk, Front Range Community College, Fort Collins, CO, for providing the idea and the instructions for this activity to Flinn Scientific.