physics hwk help please..?

Question

A bubble with a volume of 1.00 cm^3 forms at the bottom of a lake that is 20 m deep. The temperature at the bottom of the lake is 20°C. The bubble rises to the surface where the water temperature is 30°C. Assume that the bubble is small enough that its temperature always matches that of its surroundings. What is the volume of the bubble just before it breaks the surface of the water? Ignore surface tension.

I thought this question involves the equation..
(P1V1)/T1=(P2V2)/T2
but I can't seem to find the right answer using this..

any suggestions/help?? thank you so much!!

Answer 1

Your equation is correct. Are you using ºK for temp? Are you properly calculating the pressure at the bottom of the lake (m*rho*h)? Are you following the same units (water density kg/m^3, pressure N/m^2, h in meters)?

Answer 2

You know, its funny I remember doing this exact problem for physics years ago, and I still remember how to do it.

You have the right equation, but you are missing some critical information - namely the pressure at the bottom of the lake versus at the top.

pressure in pascals = density of water in kg per meter cubed * g * height of water

101325 pascals = 1 atmosphere = 760 torr

So now we can get the pressure at the bottom in atmospheres.

presssure = 1000 kg/m^3 * 9.8 * 20 meters = 196000 pascals

That's 1.934 atmospheres when I divide by 101325.

Of course, that is only the pressure exerted by the water. Above the water is the atmoshere, which exerts an additional atmosphere of pressure.

So

2.934 atmospheres is your pressure at the bottom of the lake.

I'm sure you can take it from here! Good luck!