MadSci Network: Chemistry |
I'm not familiar with the trick, but you seem to be asking two questions - why the pressure is equal everywhere inside a balloon, and how to measure the tension of a balloon.
Firstly, air particles are moving randomly and quickly all through the balloon. The pressure is caused by the collisions of the particles with each other and with the walls of the balloon. Because they are random moving in all directions, the pressure is the same in all directions.
Secondly, the best I can think of is this: Part 1Draw a 1cm square on a flat balloon (same brand and shape as the one you cut up), then inflate the balloon. When it gets to the size you want, find the new lengths of the sides of the square. If its too rounded for a ruler now, use a bit of cotton to measure the sides. Find the extension of each side, and use your graph to find out the tension which produces that extension. If your sides have stretched different amounts, you can find the average of the two (or four) tension values. That would be the tension in your balloon.This is a very approximate value that you are getting, but its the best I can think of for your grade level. If you wanted to improve it, you could draw several squares on different parts of the balloon and find an average.
Try the links in the MadSci Library for more information on Chemistry.