Ghost Bubbles (Kyra Grzywacz)

Title: Ghost Bubbles-Using dry ice to make bubbles filled with carbon dioxide gas.

Principle(s) Investigated: (several different principles can be investigated)

• Students will be able to visualize the fluidity of the cell membrane
• Students will be able to visualize the semipermeable nature of the bubble which is similar to that of a cell membrane.
• Students will be able to understand how the polar molecules of soap align them selves with the hydrophilic end of the molecule interacting with the water and the hydrophobic end of the molecule interacts with the air.
• Students will understand that soap lowers waters surface tension.
• Students will be able to visualize that the bubble forms a sphere which allows it to have the lowest surface area to volume.
• Students can visualize that white light can be broken down into its components with constructive and destructive interference.

Standards:

Cell Biology

1. The fundamental life processes of plants and animals depend on a variety of chemi­cal reactions that occur in specialized areas of the organism’s cells. As a basis for understanding this concept:

a. Students know cells are enclosed within semipermeable membranes that regulate their interaction with their surroundings.

7th grade Physical Principles in Living Systems (Physical Sciences)

e. Students know that white light is a mixture of many wavelengths (colors) and that retinal cells react differently to different wavelengths.

f. Students know light can be reflected, refracted, transmitted, and absorbed by matter.

Materials:

• A plastic jar with a lid (I used a pretzel jar)
• A container to hold dish soap
• Rubber tubing
• Dish Soap
• Dry Ice
• Warm Water
• Optional : A threaded nozzle is recommended however I did not use one.
• Glycerin added to the soap (makes better bubbles)

Procedure:

1. After obtaining a plastic container cut a small whole a few inches from the top of the container the size and shape of your tubing.
2. Insert the tubing into the whole the tubing needs to extend into the container just a few inches.
3. Fill the container 1/2 way with warm tap water.
4. Fill a cup or bowl with 4 tbsp's of dish soap and 1/2 a cup water (can also add 1 tbsp of glycerin)
5. Add the dry ice to the container with the water and place the lid on the container but do not completely close the lid leave it open enough to allow some pressure to escape.
6. Soap up the hands of the individual who wants to bounce the bubble.
7. Dip the end of the tubing into the soap and pull it our slowly and ghostly bubbles will form.
8. Have the student who is handling the bubbles observe the bubbles size intailly and then after a few seconds.
9. Reapeat bubble making.

Students Prior Knowledge:

• Prior to the experiment the student must understand that a cell is enclosed in membrane- a lipid bilayer. The student should also understand that the cells membrane is understood to function in a liquid mosaic model. The students should also understand the function of the membrane as it protects the cell but also is a semi-permeable membrane which is selective to what it allows to pass through.
• Students must also understand the concepts of a molecules with hydrophilic and hydrophobic "ends".
• Prior knowledge must include surface tension, sphere shape, and surface area.
• Lastly to use the bubble as a means to demonstrate the components of white light, students must already be introduced to the components of white light and also what transmission is.

Explanation:

Dry ice is frozen CO2 is added to warm water this allows the dry ice to sublimate (solid to gas with no liquid stage). The fog seen in the container is not carbon dioxide but instead is water vapor the extreme cold temperature causes water vapor to condense from the air. The newly created gas takes up more room than the solid dry ice. This cause carbon dioxide and water vapor to escape from the container out through the tube. The tube dipped in the soap can then create a bubble with carbon dioxide in the inside.

Almost as soon as the bubble is formed the bubble shrinks because of diffusion of the carbon dioxide across the semi-semipermeable membrane.

To show the bubble as a fluid mosaic model the colors appear to move around which gives a visual representation of movement. To show the fluid mosaic model a needle can be dipped into soap and inserted into the bubble without it poping.

To demonstrate the polarity of the soap bubbles in comparison with the cell membrane a visual diagram should be used for each and discussed.

The bubble can also demonstrate how white light is broken up due to the transmission of the light from air to a different medium. Because some light rays are reflected and some are transmitted into the soap this allows for the seperation of the visible light.

Questions and Answers:

1. Based on what you saw can you name how the polar molecules of the soap bubbles are different from the polar molecules of the the cell membrane?
2. Answer: In the soap bubble the hydrophylic part of the soap molecule is facing in towards the center of the membrane and the hydrophobic part is facing the environment inside the balloon and outside the balloon, whereas in a cell membrane the hydrophobic part of the molecules are in the center away from the environment and the hydrophylic part of the moleules interact with the environment.
3. Why do you think the bubble decreased in size after only a few seconds?
4. Answer:Just like a cell membrane the bubble is semi-permeable and the carbon dioxide leaves the bubble through diffusion.
5. As the bubble "aged" what did you notice about the colors?
6. Answer: As the bubble "ages" the bubbles wall thins. The walls become so thin that interference is no longer created, all wavelengths are cancelled out. When this happens the bubble seems colorless
7. What phases did you see the dry ice go through?
8. Answer: Dry ice goes through a process called sublimation which is a process when a substances goes from a solid to a gas state (skipping the liquid state).
   1. Applications to Everyday Life:
9. Rainbows are a beautiful part of our "everyday" life introducing students to the the concepts of how a bubble is capable of breaking up visible light into its components allows you to relate it to the "rainbows" the student sees. This can help a student find interest in science because it is an ocurence they can explain to others.
10. We are all made of cells and understanding how the cells membrane works can help students understand diseases dealing with cell membranes. Some examples are: Alzheimer's and Cystic Fibrosis.
11. Soaps hydrophilic head and hydrophobic tails allow it to clean things such as are clothes. The grime is held within the micelles soap form.

Photographs:

Videos:

http://www.youtube.com/watch?v=pP_lZaOchE0&feature=player_embedded

References:

http://www.stevespanglerscience.com/product/boo-bubbles

http://chemistry.about.com/od/dryiceprojects/a/dryicebubble.htm

http://chemistry.about.com/od/bubbles/a/bubblescience.htm

http://www.exploratorium.edu/science_explorer/bub_dome.html

http://www.bubbles.org/index.htm

http://www.webexhibits.org/causesofcolor/15E.html

Photos in presentation:

http://www.ischool.zm/bio/Ch.%201%20Cell%20Structure%20and%20Organisation.htm

http://www.nanonics.co.il/patch-clamping-ion-conductance.html

http://www.enotes.com/topic/Cell_membrane

http://www.biologypictures.net/page/3/

http://www.brooklyn.cuny.edu/bc/ahp/LAD/C4d/C4d_phospholipid.html

http://commons.wikimedia.org/wiki/File:Lipid_vesicle_vs_soap_bubble.svg