Why does a balloon filled with helium rise while a balloon filled with an equal volume of average atmosphere air does not?

Answer 1

The effect is a result of the difference between the density of the gas within the balloon and the density of the gas outwith the balloon, such that a buoyant force is created that can overcome the gravitational forces upon the balloon.

To create a buoyant force, the gas within the balloon must be less dense than the gas outwith the balloon. The gas outwith a balloon is air (atmosphere) which roughly contains 78.09% nitrogen, 20.95% oxygen, 0.93% argon, 0.039% carbon dioxide, and small amounts of other gases. Helium is less dense than this combination of gasses, thus if we release helium into the atmosphere, it automatically rises through the atmosphere. Although gravity has an effect upon this gas, the buoyant force can easily overcome it. It will continue to rise until the density of the surrounding gasses is equalised at which point it will hover, neither rising nor falling to any significant degree.

A balloon makes use of this buoyant force by trapping the lighter gas within its envelope. Although the weight of the balloon itself adds a greater gravitational force, the buoyant force of the gas within can easily overcome this. If nothing else, this demonstrates just how weak gravity really is -- even a noble gas can easily overcome it!

We can achieve the same thing with air itself. Hot air is less dense than cold air (hot air rises, after all), thus if we can heat up enough air within an envelope we can make the envelope rise upwards. Since heat will be lost through the envelope, we must ensure a constant supply of hot air is provided. Thus the balloon needs to be sufficiently large enough to accommodate enough hot air to lift both the envelope and the burner that heats the air. Chinese lanterns are a classic example of this type of hot air balloon. In order to lift people and other objects, we simply need a much larger envelope. Manned hot-air balloons are simply extremely large Chinese lanterns, using propane gas burners to heat the air in the envelope.

The materials used in the balloon obviously need to be as light as possible, hence the envelope is constructed from ripstop nylon or dacron, while the gondola or basket is typically made from woven wicker. The burner and propane gas bottles are the heaviest elements, besides the people being carried. The combined weight of a 5-passenger hot air balloon can still be more than 3.5 tons. Even so, 100,000 cubic feet of hot air (weighing almost 6000 lbs) is enough to lift this enormous weight.

Answer 2

A helium balloon rises into the air because the density of the helium is lesser than the density of the air, therefore, the balloon rises, trying to reach above the air.

Helium is lighter than air, or to be more precise, less dense.

Helium gas weighs less than our atmospheric air so it floats. Same goes for hydrogen and a few other pure gases

Answer 3

Density of an object = mass / volume

Firstly, this depends on what we inflate the balloon with. An object that floats without producing an upwards force must be less dense than air, and air is not very dense at all.

Say the balloon has not been inflated. Therefore its density is quite high compared to air: solids and liquids will almost always be more dense than air, therefore land does not float into the sky and seas stay where they are.

Now say it is inflated with air. The balloon will have much lower density as a whole because the air inside has a low density. However, this balloon will not float because its density will definitely be larger than air because of the balloon material it is made of. It may, however, slow the rate at which it falls because it is similar in density to air, but will not float.

The only way to make a balloon float is to make it less dense than air, as we said, and air is mainly made of nitrogen (approx 80%) and oxygen (approx 20%). Therefore, if filled with a sufficiently low-density gas the overall density will be very small. Helium is a good option: it is unreactive and the second lightest element, perfect for inflating balloons. The density will be the sum of the helium's mass and the balloons mass divided by the volume of the balloon, and if enough helium is pumped in it will become less dense than air and float.

NB: Hydrogen can also be used, but is not recommended as demonstrated by the Hindenburg disaster

Answer 4

A balloon filled with helium will rise because of its density, which is the ratio of the mass and volume. The density of a helium filled balloon is less than the density of the surrounding air, which creates a pressure difference, causing the balloon to rise.

In a helium tank, the helium is greatly compressed, so has greater mass within the volume of the tank. The tank also weighs significantly more than the balloon. The result is that the density of the tank plus its contents is much greater than that of the surrounding air.

Answer 5

A balloon filled with helium rises because helium is less dense than the surrounding air, creating a buoyant force. In contrast, the air inside a balloon is the same density as the surrounding air, so there is no buoyant force to lift it.

Answer 6

Balloons rise when they are filled with something that is less dense than air, like helium. In other words, the gas in them is lighter than the rest of the air.

Answer 7

Helium is lighter than air. More precisely, it is less dense.

Answer 8

Helium is lighter than air.It make a balloon rise.

Answer 9

Because helium is lighter than air.