Calculating the diameter of a bubble

  • Thread starter jdawg
  • Start date
  • #1
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!
 

Answers and Replies

  • #3
367
2
Ok! That makes more sense. So how do you find the coefficient of surface tension?
 
  • #4
haruspex
Science Advisor
Homework Helper
Insights Author
Gold Member
2020 Award
36,411
6,941
Ok! That makes more sense. So how do you find the coefficient of surface tension?
Did you try the link I posted?
 
  • #5
367
2
Does that formula only work for water though? Is there a formula like that for soap?
 
  • #6
haruspex
Science Advisor
Homework Helper
Insights Author
Gold Member
2020 Award
36,411
6,941
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
367
2
Then you could use that formula?
 
  • #8
haruspex
Science Advisor
Homework Helper
Insights Author
Gold Member
2020 Award
36,411
6,941
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.
 
  • #9
367
2
I'll give it a shot, thanks for your help!
 

Related Threads on Calculating the diameter of a bubble

Replies
14
Views
60K
Replies
4
Views
2K
  • Last Post
Replies
2
Views
3K
  • Last Post
Replies
2
Views
922
Replies
5
Views
6K
Replies
8
Views
5K
Replies
2
Views
761
  • Last Post
Replies
3
Views
3K
Top