Helium Balloons are a popular decoration at many events, such as birthday parties and weddings. They are also popular with children, who enjoy holding them (and letting them go). When a helium balloon is released it floats and rises in the air. Have you ever wondered why this occurs? Read this article to find the answer.
Why does a helium balloon float in the air?
When a balloon is inflated using normal air it does not rise unless it is thrown into the air and it quickly returns to earth. However, if you inflate a balloon using helium it will quickly rise through the air. The simple reason for this is that helium is lighter, or more correctly less dense, than air. A helium filled balloon will essentially float on the air.
A good way to explain this idea is to think about floating and sinking. When an object such as a beach ball is placed into water it pushes away some water. The force of the water pushing back into that space is greater than the force of the beach ball pushing down and this means that the beach ball stays afloat. If a heavy object such as a rock is placed in the water the force of the water pushing back into the space is to enough to equal the force at which the rock is pushing down so it sinks.
The reason that a helium balloon floats is that helium is a gas that is much less dense than air. The molecules that make up helium are smaller, lighter and take up less space that air, which makes it less dense than air. The force of a helium filled balloon pushing down on the air is not enough to counteract the force of the air pushing it up. These causes the helium balloon to rise or float just like the beach ball. A balloon full of air sinks because the mass of the air inside the balloon is greater than the force of air outside the balloon. So it sinks because the air pushing back into the space does not have enough force to stop the fall of the balloon.
The following further explains this phenomenon: