Re: When you put sulfuric acid and baking soda together why do bubbles float?

I'm not sure if the questioner is asking why bubbles float specifically in a
wafer+sulfuric acid solution (and not pop?), OR, why bubbles float in
general??  I may be misunderstanding the question.  Here are my attempts at
an answer.

a) Why bubbles float in water+sulfuric acid solutions, and not pop?:
This is tough to answer with any exactness.  Whether one gets bubbles or not
depends on the viscosity and/or surface tension of the solution at hand.
There is no way I know of to simply explain this for general water+sulfuric
acid solutions. Viscosity & surface tension are tough concepts to explain to
a 7th-9th grader.  Why bubbles float?, see (b) below.

b) Generally bubbles float because the gas or vapor they contain is of lower
density than that of the liquid they are floating in. Density is defined as
the mass per unit volume of a substance (mass/volume).  For example, lead
(Pb) has a high density as a small volume of Pb is heavy.  On the other hand
helium (He)has a low density as a large volume of He weighs less than an
identical volume of air (why He balloons float).  A 7th-9th grader can learn
more about density from a high school chemistry book, general science book 
(high school or middle school level), or ask a science teacher.