Lower air pressure in the surroundings will cause helium gas to escape at a faster rate, from a balloon.

Diffusion - is the transfer of molecules from an area of high molecule density to an area of lowerdensity. In this experiment diffusion occurs when the helium gas molecules inside the balloon (are of high molecule density) move out into the airspace surrounding the balloon. The air pressure of the room in which the experiment is conducted, is varied by repeating the experiment on different levels of a tall building.

The hypothesis is proven to be true. Higher floors have a lower atmospheric pressure and therefore lower air density. This causes the helium gas which is at a higher density to escape more rapidly due to diffusion. The helium gas is able to escape through microscopic holes that naturally exist in the walls of latex balloons. These small holes are larger than helium atoms. It is because of diffusion, that balloons grow smaller over time.

These helium balloons are commonly used in parties and are extremely popular with children. In more advanced applications, they are also used to gather data for weather forecasting.

What would happen if the experiment was conducted using other types if gases?

How will different room temperatures affect your results? What happens if you vary the humidity levels of the surrounding air?