1. The problem statement, all variables and given/known data 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? 2. Relevant equations ΔP=4Y/R 3. 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!