Departments : Integrating Science in Your Classroom :
Soda Bottle Science
By John Cowens
A common two-liter plastic bottle becomes a miniature science lab in these fun experiments
Online Extra: Soda Bottle Science Experiments
I enjoy walking my Boston terrier alongside rural roads while collecting soft-drink bottles that have been tossed into drainage ditches. I bag the bottles, take them to a local grocery store and collect a nickel for each. This money is used to buy reward pencils for my students. There are times, however, when I save a few clear plastic two-liter bottles for the purpose of performing science experiments with my students. Of course, these bottles must be thoroughly cleaned and sterilized before using them in my classroom. As a safety precaution, it's best to have students donate empty, sanitized two-liter bottles that come from home.
These experiments use clear plastic two-liter bottles, which make perfect miniature science labs.
Experiment #1: Density of liquids
Water molecules are constantly in motion. This bouncing and bumping of molecules is called "diffusion," which also occurs in gases and solids. Diffusion in our air causes fragrances to spread all around a room (i.e., flowers, cologne, cooking odors, etc.).
Materials:
- water
- food coloring
- scissors
- two-liter plastic bottle
Procedure:
- Cut the top 7.5 cm off the bottle.
- Fill the bottle about 3⁄4 full with water.
- Carefully drop 5-7 droplets of food coloring into the bottle of water.
- Observe how the food coloring falls to the bottom of the bottle, leaving peculiar trails.
- Let the bottle sit undisturbed for a few hours. What happened to the trails?
Experiment #2: Homemade lava lamp
Years ago, lava lamps were the coolest devices to own! For hours one could easily sit and stare at the colorful globs as they slowly moved up, down, fused together and separated into extraordinary shapes. What were these bizarre globs?
Materials:
- two-liter plastic bottle
- vegetable oil
- food coloring
- water
Procedure:
- Pour vegetable oil into the bottle until it is 1⁄3 full.
- Add 3-4 drops of food coloring.
- Carefully fill the bottle the rest of the way with water and tighten the cap.
- Allow enough time for the water and oil to separate.
- Slowly rock the bottle back and forth and observe the wave action.
- Slowly tip the bottle until it is upside down and observe the same lava lamp effect.
Explanation:
Water is denser than oil. This makes water stay on the bottom of the container while oil "oozes" to the top. Changing the temperature of these liquids has interesting effects, too!
Experiment #3: Lung simulator
Your spongy, elastic and expandable lungs are located in your chest cavity and protected by a strong rib cage. When you inhale, the diaphragm and intercostal muscles contract and expand the chest cavity. This expansion lowers the pressure in the chest cavity below the outside air pressure, draws air in through the airways and inflates the lungs. To exhale, the diaphragm and intercostal muscles relax, air flows out and the chest cavity gets smaller. This decrease in volume of the cavity increases the pressure in the chest cavity, which is higher than the outside air pressure. High-pressure air from the lungs then flows out of the airways to the outside low-pressure air.
Materials:
- 10" to 12" party balloon
- punch balloon
- two-liter plastic bottle with the bottom cut off
- rubber band
- cellophane tape
Procedure:
- Cut the nozzle end off the punch balloon and slip it over the bottom of the plastic bottle, leaving a little slack. Secure the punch balloon with cellophane tape. (The punch balloon represents the diaphragm.)
- By holding onto the nozzle of a balloon, stuff the remainder of the balloon through the bottle's mouth.
- Secure the party balloon's nozzle around the mouth of the bottle with a rubber band. (The balloon represents the lungs and the bottle represents the chest cavity.)
- Pull down on the punch balloon (diaphragm) and observe what happens to the balloon (lungs) inside the bottle! Release the diaphragm.
- Push the diaphragm into the bottle and carefully observe what happens to the other balloon (lung).
Online Extra: Soda Bottle Science Experiments
John Cowens teaches sixth grade at Fleming Middle School in Grants Pass, OR.
November/December, 2006 Volume 37, Number 3
