Title: Cartesian Divers
Principles Investigated: Buoyancy, Boyle’s Law, and Pascal’s Law
Standards: CA Content Standards for Science
· Grade 8: Physical Sciences
· Grades 9-12: Chemistry
Materials:
Procedure: This lesson will take one-to-two 55 minute class periods. The experiment and Worksheet 1 take one period. Worksheet two can be homework, a quiz, or used as class work during the second period prior to a class discussion. A summative evaluation for this assignment is attached, and is designed to test all levels of Bloom’s Taxonomy.
Day 1:
1. Distribute all materials except droppers (students will be distracted by them).
2. PowerPoint with lecture introducing everyday examples of Boyle’s Law and Pascal’s Law. (2-3 minutes)
a. (Explain what each thing does but do not explain what the laws are at this time.) A metal submarine cruises deep in the ocean, then rises and surfaces. Bubbles from a diver grow larger as they near the surface. A hospital nurse pulls the plunger on a syringe and blood leaves a patients arm. A family drives down a mountain and all of their ears pop. A father presses down on a pump handle and air enters his child’s bicycle tire. A bus driver presses on a pedal and the bus slows down. A speaker expands his chest and air moves into his lungs. (In Powerpoint)
3. Instruct students to discuss the following question with a neighbor. “What do these have in common?” (2-3 minutes)
4. Next, discuss as a class. ( 2-3 minutes)
5. Distribute Worksheet 1. Each individual must complete a worksheet during group experiments.
6. Show video on how to setup the experiment and allow for questions. (5 minutes)
7. Remind students of the difference between observation and inference. (1 minute)
8. Distribute droppers and announce “begin”.
9. Students work in small groups conducting experiment and recording observations on Worksheet 1. (10-20 minutes)
10. Class discusses observations. (5 minutes)
11. Clean-up
Day 2:
1. Distribute Worksheet 2. Instruct students to complete Worksheet 2 individually, and to answer questions as completely as possible using their data from Worksheet 1.
2. Show Boyle’s Law and Pascal’s Law on overhead for students to record on Worksheet 2.
3. Allow time to complete Worksheet 2. It can be class work, homework, or a quiz. (15-25 minutes)
4. Students compare Worksheet 2 answers in groups. (5 minutes)
5. Class discussion based on both worksheets. (5-10 minutes)
Student Prior Knowledge:
Buoyancy (Archimedes’ Principle): The resultant upward forces exerted by the water on a submerged or floating body, equal to the weight of the water displaced by this body.
Explanation:
This version of the Cartesian Diver demonstrates Archimedes’ Principle, Boyle’s Law and Pascal’s Law. Students should already be familiar with buoyancy (Archimedes’ principle).
Pascal’s Law states that pressure supplied to an enclosed fluid is transmitted undiminished to every portion of the fluid and to the walls of the containing vessel. In layman’s terms, if pressure is applied to a closed container of fluid, the pressure will be distributed evenly, everywhere in the container. The Cartesian divers in this experiment are inside of a closed container of fluid. As the container walls are squeezed, the pressure is distributed evenly throughout the fluid—it is even transmitted to the fluid inside the divers (observe clear water entering tip), compressing the gas therein (Boyle’s Law).
Boyle’s Law states that at a constant temperature, the volume of a fixed amount of gas is inversely proportional to pressure. In layman’s terms, if the temperature does not change, a sealed amount of gas takes up an amount of space that shrinks consistently as pressure goes up; as pressure goes down the amount of space occupied by the gas grows consistently. The Cartesian divers in this experiment contain a gas—the air bubble trapped inside the dropper. The pressure applied to the container of water is transmitted evenly inside the droppers (Pascal’s Law). The increased pressure in the droppers pushes on the bubble, and the space occupied by the gas shrinks. As the bubble gets smaller more water goes inside the dropper, which changes the weight of the fluid displaced by the dropper, changing the buoyancy, and causing the diver to “dive.”
Questions & Answers
Applications to Everyday Life:
Photographs:
Videos:
http://www.youtube.com/watch?v=OR6G0K3JEeg
References:
Benson, T. (2010, July). Gas Pressure. From NASA K-12 Education. http://www.grc.nasa.gov/WWW/K-12/airplane/pressure.html (Accessed 2011, February 2).
Daily Motion. How to Make a Submarine. http://www.dailymotion.com/video/xgh4pw_how-to-make-a-submarine_lifestyle (Accessed 2011, February 2).
Dictionary.com. http://dictionary.reference.com/ (Accessed 2011, February 2).
Heiszwolf, J. Submarine Dive Technology. http://www.heiszwolf.com/subs/tech/tech01.html (Accessed 2011, February 3).
Herr, N. (2008). The Sourcebook for Teaching Science: Strategies, Activities, and Instructional Resources. San Francisco: Jossey-Bass.
Huetinck, L., & Adams, S. (2001). Physics. New York: Wiley Publishing, Inc..
Kid’s Science Experiments. http://kids-science-experiments.com/cartesiandiver.html (Accessed 2011, February 1).
Making a Cartesian Diver Toy. http://www.chemistar.com/Student/CartesianDivers.pdf (Accessed 2011, February 2).
Physlink. Physics and Astronomy Online. http://www.physlink.com/education/askexperts/ae518.cfm (Accessed 2011, February 3).
Question Hub. Questions and Answers from Around the Web. http://www.questionhub.com/YahooAnswers/20070903122014AA9qQPF (Accessed 2011, February 2).
Science Dictionary. http://www.sciencedictionary.org/ (Accessed 2011, February 2).
Wikipedia. Cartesian Diver. http://en.wikipedia.org/wiki/Cartesian_diver (Accessed 2011, February 2).
Wikipedia. Boyle’s Law. http://en.wikipedia.org/wiki/Boyle%27s_Law (Accessed 2011, February 2).
Wikipedia. Pascal’s Law. http://en.wikipedia.org/wiki/Pascal%27s_law (Accessed 2011, February 2).