Hot Air Balloons: The Science Behind How They Work

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How do Hot Air Balloons Work?

Hot air balloons and blimps are able to fly because the gases used have several different physical characteristics. These gases can change with differing temperatures, and the density of the gas fluctuates. This gives the balloon or blimp buoyancy, or the ability to float. Helium and other gases have lower molecular weights that force them upward, through the denser gases. These molecules remain spread far apart from each other, which encourages them to lift upward. When the volume of air is increased, and the density of the air is decreased, it pushes that hot air upward.

Resources and Experiments about Hot Air Balloons
E-Balloon and photos
Hot Air Balloon Experiment
Build Your Own Balloon – How to make your very own hot air balloon!
Hot Air Balloon Facts – Some interesting facts about the history of hot air balloons.

There are three basic phases of matter.

Of these three, gases have the most stored energy, while solids have the lowest. Solids have a definitive shape and volume, and liquids do not have a definite shape. With gases, there is no definite shape or volume, so the molecules are held together simply by force. A gas molecule can travel as fast as 1,000 miles per hour when present in standard temperature and pressure. At this extremely fast speed, the gases are colliding, which scatters them into different directions.

Resources and Experiments about the Phases of Matter
What a Gas! – An experiment for K-4 that shows how gases work.
Fun With Gas

What is Helium?

Helium is a colorless, odorless gas that is most commonly used in small balloons to make them float. This gas has also been used as a source of fuel for the US military. It has a very low atomic mass, which is the main reason it is so light and why it causes objects to float.

Resources and Experiments about Helium
Experiments with a Helium Balloon

>What is Density?

Density is essentially how close molecules are spaced together. Another way to look at density is an objects weight. Items with higher density can be the same size as something with a lower density, they will just weigh more. For example, an element such as metal has a high density, while gases are lower in density. If something has low density, it tends to be lighter and a lot more sparsely spread. This is why hot air balloons use gases to help get them up in the air.

Resources and Experiments about Density
Three Layer Float Experiment
Liquid Density Experiment
Multiple Density Experiments

What is Buoyancy?

Buoyancy is basically an object or matter’s ability to float in water. Technically, it is the upward pressure or force caused by the fluid underneath of the object which in turn causes it to float. Density plays a role because the density, or weight, of an object can affect its buoyancy. The forces of the water pushing an object up to cause it to float can be compared to how hot air balloons float. The lighter the object and the force of the gases combined cause the balloon to rise up and seem to carelessly float along in the air.

Resources and Experiments about Buoyancy
Experiment with Buoyancy Ship Experiment
Floating & Sinking
Making a Penny Float Experiment

Resource by B.Sobey

I am a recent masters graduate from FL. I enjoy the beach, traveling, and writing. I just moved to South Carolina in hopes to find a job as a journalist.

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