Calculating the diameter of a bubble

In summary, the conversation discusses finding the diameter of a soap bubble with a pressure increase of 40 [Pa] when the temperature is 80℃. The formula ΔP=4Y/R is mentioned, but there is confusion about how to find the coefficient of surface tension (Y). It is suggested to use the Eötvös rule for water, but it is uncertain if it applies to soap. It is also suggested to estimate the critical temperature for the soap solution and use that to find the coefficient of surface tension at 80℃. However, this approach is not confirmed. Overall, the conversation explores different methods for finding the coefficient of surface tension and its relation to temperature.
  • #1
jdawg
367
2

Homework Statement


Suppose the temperature is 80℃ and we have a soap bubble that has a pressure increase of 40 [Pa]. What is the diameter of the bubble?

Homework Equations


ΔP=4Y/R

The Attempt at a Solution


I'm very confused about how to find the coefficient of surface tension (Y).
In an example my professor gave us in class he gave us Y(20°C)= 0.0728 N/m. So I'm guessing the coefficient changes with temperature? How would I calculate Y(80°C)? Is there a formula I'm missing?

Also I saw a different version of the above formula where they had ΔP=4T/R. Under what condition would you be able to just neglect the coefficient of surface tension and plug the temperature straight in? Or maybe is that formula completely incorrect? Thanks!
 
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  • #3
Ok! That makes more sense. So how do you find the coefficient of surface tension?
 
  • #4
jdawg said:
Ok! That makes more sense. So how do you find the coefficient of surface tension?
Did you try the link I posted?
 
  • #5
Does that formula only work for water though? Is there a formula like that for soap?
 
  • #6
jdawg said:
Does that formula only work for water though? Is there a formula like that for soap?
What if you assume that the difference between water and a soap solution is due to a difference in the critical temperature?
 
  • #7
Then you could use that formula?
 
  • #8
jdawg said:
Then you could use that formula?
Yes. You could use the given datapoint for the soap solution and the formula to estimate the critical temperature for that soap solution. Then you could find the water temperature that should have the same coefficient as the soap solution at 80C.
Mind you, this is just guesswork. I have not been able to find any info online to confirm this approach.
 
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Likes jdawg
  • #9
I'll give it a shot, thanks for your help!
 

FAQ: Calculating the diameter of a bubble

1. How do you measure the diameter of a bubble?

To measure the diameter of a bubble, you will need a ruler or caliper with millimeter measurements. Gently place the bubble on a flat surface and use the ruler or caliper to measure the distance across the widest part of the bubble. This will give you the diameter in millimeters.

2. What is the formula for calculating the diameter of a bubble?

The formula for calculating the diameter of a bubble is: D = 4 * V / π, where D is the diameter and V is the volume of the bubble. To calculate the volume of a bubble, you can use the formula: V = (4/3) * π * r^3, where r is the radius of the bubble.

3. Can the diameter of a bubble change?

Yes, the diameter of a bubble can change. As the bubble floats and floats, the air inside it expands and contracts, causing the diameter to change. External factors such as temperature and humidity can also affect the diameter of a bubble.

4. How accurate is the measurement of a bubble's diameter?

The measurement of a bubble's diameter can be accurate to a certain degree, but it may not be completely precise due to the fluctuation and fragility of bubbles. However, with careful measurements and multiple trials, you can get a fairly accurate estimation of the bubble's diameter.

5. What other factors can affect the diameter of a bubble?

Aside from internal and external factors, the type of solution used to create the bubble can also affect its diameter. Soap solutions with different concentrations or different types of soap can produce bubbles with varying diameters. The surface tension of the solution and the strength of the bubble wand can also play a role in the diameter of a bubble.

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