Can you be more specific?

Your poblem is not in the ideal gas ecuation but in the evaporation process. that is : how many molecues (moles) are forming the gas; that will depend on pressure and temperature mainly (there will be a dependence on volume and time in the general case but if the process is fast eneugh they may be negligible in a first approximation), 

Presssure inside the buble will not be the same as the persure un the rest of the vluid due to surface tension.

Dear Shiuh-Hwa Shyu,

In order for streamer to be initiated in a microbubble, localised electric strength (inside the bubble) needs to be larger from the dielectric strength of the material of the bubble (say, Methane) The microbubble (in liquid dielectric e.g. transformer oil) itself developed through several means such as localised joule heating, Dielectric strength of the material turn out to be affected by temperature (T) and pressure (P). However T is unknown. Previously I tried out ideal gas equation and I found out that a second parameter, moles of gas inside the micobubble is also unknown. To make things more confusing, moles are also affected by P and T. Then I started to think that maybe my interpretation or understanding of ideal gas equation is wrong.

Gabriel Garcia Soriano had suggested that it is evaporation process that I should look into. Now I'm going back to text book again.

Dear Azharudin Mukhtaruddin,

Other than the ideal gas model, what other equations are you solving? Have you considered solving the continuity, momentum, and, especially the energy equations?

Dear Shiuh-Hwa Shyu,

So far I've only tried the ideal gas model. Perhaps I should explore other methods as well.

Thank you for all the suggestions.