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Transcript of BUBBLES!
Why Bubbles Pop
Connections to Life
Experiment Surface Tension - “Surface tension is a contractive tendency of the surface of a liquid that allows it to resist an external force”
- Tendency to minimize wall tension pulls bubbles into spherical shape
- LaPlace’s Law: the larger the radius of the bubble, the larger the wall tension required to withstand internal pressure
- Spherical shape minimizes surface area = requires least energy to achieve
- Detergent molecules cover surface of bubble, letting it get a lot bigger without breaking Structure - Thin film of soapy water
- 3 layers – soap, water, soap
- Soap molecule is hydrophilic on one side and hydrophobic on the other
- Hollow sphere with shiny surface
- Soap stabilizes bubble Bubble Colours - Due to interference of light waves reflected and refracted
- Depends on thickness of bubble
- Thinner – appear darker (light reflected from inner and outer layers cancel out)
- Thicker – display vibrant colours separated out of white light (light from inner and outer layers combine) Why Bubbles Pop - Hits something dry
-Drainage within the soap film Bond Angles - If films meet along common edge, angles are all 120 degrees Shape - Surface tension tries to shrink the bubble into a shape with the smallest possible surface area for the volume of air it contains
- That shape is a sphere Connections to Everyday Life -Soap-water-soap layer is similar to the lipid bilayer that forms the membrane around each cell in the body
-The lipid bilayer is composed of hydrophilic and hydrophobic molecules, just like the soap Experiment BUBBLES! Presentation by Emmanuel, Mariam, Geli and Anna Blow Me
(One More Sphere) Why Detergent? More Science -Antibubbles
- The Marangoni Effect - detergents will form bubbles even in tap water
- contains ions that could prevent soap bubble formation
- extends life of bubble by forming weak hydrogen bonds with water
- slows down evaporation And so…:
Why did adding salt prevent bubbles from forming?
Why do hand lotion and sugar make better bubbles? 3. What is the best thing to add? (Continued) Comments:
Sugar produced some bubbles that never burst!!!
Food coloring does not really make bubbles colorful…
Adding lotion made it a real challenge to blow bubbles but the bubbles made were very successful.
Salt and baking soda prevented a film from forming on the wand so no bubbles could be made. 3. What is the best thing to add? (Continued) Observations: 3. What is the best thing to add? (Continued) Conclusions:
The best ratio is 10 parts water, 1 part detergent.
Below this ratio, the bubbles do not last as long and they are not as strong. Above this ratio, the bubbles’ performance begins to decline.
These were very unexpected results: we thought that more detergent would improve the durability of the bubble. 1. What is the best detergent to water ratio? Purpose
Variables we are testing:
Judging the bubbles:
Average time it lasted
Can they bounce?
Easy to blow?
Pretty? (Mariam standards, not Emmanuel!) Introduction Experiment:
The quest for the perfect bubble!
10 parts water at room temperature
1 part dish detergent
Glycerol THE BEST SOAP BUBBLE SOLUTION! Conclusions:
Adding sugar and hand lotion makes the most durable bubbles.
Some substances like salt prevent bubbles from forming.
Judging by time only: 3. What is the best thing to add? (Continued) Standard solution: 10 parts water, 1 part detergent, water at room temperature, 1 teaspoon of substance added.
Observations: 3. What is the best thing to add? Observations:
Several recipes call for warm water but our experiments show that room temperature is ideal.
Using cold water decreased the strength of the bubbles a lot more that what we expected. 2. What is the best water temperature to use? Observations:
1 part = 1 tablespoon 1. What is the best detergent to water ratio?