Re: Will humidity affect a balloon that's on a white or black bottle?

I'm not exactly sure what you are asking here, but I'll try to give it my best.

I think that any humidity effects are going to be too small to observe. 
Humidity may affect the elasticity (stretchiness) of the balloon, but I
think that won't be affected on a short time scale (in other words, if you
store it for a long time in dry conditions, in might become more brittle
than if you left it around humidity - but nothing you'd see different over
a few hours or even a few days).

Humidity can affect pressure - humidity is a measure of how much water
exists in the air as a gas.  According to the Law of Partial Pressures,
this could change how hard the air in the bottle is pushing on the balloon
as it is heated, but that would be a fairly complicated case (and is
probably not something you'll learn about until high school physics.)
However, even the water vapor is a gas and so the total pressure would
still be roughly the same as dry air.  (The total atmospheric pressure
differs according to the humidity, but you're trying to detect changes,
so the starting pressure is not of interest, I think!)

I hope that helps, if not, feel free to ask again, but include:
 - what is inside the bottle/balloon?
 - what are you doing to them both?
 - are you comparing this to something else (another bottle/balloon?)?
 - what are you trying to observe (and what is your prediction, if you
have one)?

These pieces will help us put the puzzle together with you!

:*)
Kevin Davies