# Balloon

#### Lightfire

Joined Oct 5, 2010
690
I found out that helium can lift one gram per liter. For example, a balloon filled with one liter helium can lift something that weighs one gram, assuming that the the weight of the balloon and its thread is negligible.

But I am very wondered on how many miles from the Earth can a specific balloon can lift a specific item.

For example, a balloon which is filled with 1000 liters helium is about to lift an item that weighs 1 kilograms.

So meaning the balloon I specified can lift 1,000 grams, or 1 kilograms, which is exactly the weight of the item specified.

So, we now know that the balloon I specified can lift the item I specified. But how many miles from the Earth?

This is very confusing. I really need the help of everybody.

Thank you very much.

#### Wendy

Joined Mar 24, 2008
23,320
Ever see high altitude balloons? They are not full full when they are launched, and the gas expands to fill the balloon as it rises into the upper atmosphere. Your hypothetical balloon is likely going to pop before it gets very high at all.

Many weather balloons are completely filled, they plan on them bursting to recover the payloads with a parachute.

#### DerStrom8

Joined Feb 20, 2011
2,390
The reason the balloons expand is because there is much less pressure the further you go into the sky. Therefore, as a balloon rises, the pressure inside the balloon becomes greater than the pressure outside. This causes it to expand and, eventually, pop.

The height that the balloon can go depends entirely on the material it is made of, how big it is, and weather conditions (especially pressure). It is impossible to say for sure how far it would be able to go before it pops.

Der Strom

#### Markd77

Joined Sep 7, 2009
2,806
At sea level a litre of helium weighs 0.18g, a litre of air weighs 1.28g so a litre of helium can lift 1.28-0.18=1.1g
At a height of 6000m air pressure, and therefore density, is roughly half so a litre of helium weighs 0.09g and a litre of air weighs 0.64g, so a litre of helium can lift 0.55g

However if you started with a litre of helium at sea level it would have expanded to 2 litres at 6000m so it can lift the same amount as at sea level.

Pressure volume temperature relationship is here:
http://en.wikipedia.org/wiki/Ideal_gas_law

How did drinking the Hydrochloric acid go?

#### Lightfire

Joined Oct 5, 2010
690
Hello everybody,

Your hypothetical balloon is likely going to pop before it gets very high at all.
Ow, I just fully filled up my balloon with helium. Meaning, if I lower the helium filled up in balloon, let's say 200 liters, it may go higher? But the problem is its capacity to lift something. In this case, my balloon can only lift something that weighs 200 grams.

The reason the balloons expand is because there is much less pressure the further you go into the sky.
Would you explain me how pressure affects the balloon, please?

Therefore, as a balloon rises, the pressure inside the balloon becomes greater than the pressure outside. This causes it to expand and, eventually, pop.
Meaning it is impossible to have a balloon that will never pop?

How did drinking the Hydrochloric acid go?
Just taste only, not drink.

#### spinnaker

Joined Oct 29, 2009
7,830
Your hypothetical balloon is likely going to pop before it gets very high at all.

.
It would depend on the material the balloon is made of. A common latex balloon is pretty porous and becomes more so as the balloon expands. It could leak gas before it pops.

#### spinnaker

Joined Oct 29, 2009
7,830
Hello everybody,

Would you explain me how pressure affects the balloon, please?

There is air pressure all around you. It is squeezing you right now You just don't feel it. It also presses on the balloon all around too. It keeps it compressed. The air molecules stay close together. As you go higher the air pressure gets less . So the balloon expands. The space between the molecules becomes bigger. The pressure in the balloon is greater than the air pressure outside so it wants to try and equalize (get outside the balloon).

You will see the opposite thing if you try and push the balloon under water. The water can exert more pressure than air so it squeezes the balloon and compresses the air in the balloon. The deeper you go, the more it compresses.

SCUBA divers need to be very aware of pressure. When they breath air, the tank automatically gives them air near the same pressure as the water around them or the pressure on them would be so great they would not be able to move their chest to breath.

The deeper they go the higher the pressure. The higher the pressure the more air molecules they breath.

If they go too deep and are breathing normal air they can get nitrogen narcoses or "the rapture". This is because most of what we breath in nitrogen. So really what they get is an overdose of nitrogen. They start acting crazy. The same effect if you got the gas mask thing from your dentist.

The other problem they have is that nitrogen is being crammed into their blood. It is OK as long as they don't go too deep as mentioned. The water pressure around them keeps the nitrogen in solution. But if they come up too fast all at once then the nitrogen comes out of solution and forms bubbles. This is called "the bends" because the bubbles will go to their joints and cause pain. The diver will bend his arms and legs to make them feel better.

This is like taking the cap off of a soda pop bottle. When the cap is on you do not see bubbles but as soon as you take the cap off you release the pressure in the bottle. This is the fiissssssssss sound you hear. it is gas escaping. When the pressure is released on the soda pop it starts to bubble.

The same thing happens to a divers blood if they come up too fast.

What divers will do is come up to the surface not faster than their smallest bubbles (from their air tank). They will also stop at a couple levels to allow the extra nitrogen to exit their bodies before coming to the surface.

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#### spinnaker

Joined Oct 29, 2009
7,830
Meaning it is impossible to have a balloon that will never pop?

See my post above it may not pop. It may leak the gas before it gets a chance to pop.

You could also have a valve to bleed the gas but then the balloon would loose it's lift.

The balloon is only going to be able to go so high before it becomes too heavy for the air around it to support it.

Remember what I said about air pressure pressing on you? Well it also presses up.

#### Wendy

Joined Mar 24, 2008
23,320
As I said, it is planned for. That is why they have a parachute.

#### Evil Lurker

Joined Aug 25, 2011
116
Interesting topic.

The earths atmosphere is a lot like an ocean of gas. Gravity is pulling down on all the gas molecules in our atmosphere, and thus the closer to the surface you get natually the greater the pressure the gas is going to be since there are all these molecules up higher pushing down. If it weren't for intramolecular forces pushing the gas molecules apart, we would have a liquified sea of gas floating on top of our oceans.

So what causes a balloon to float anyways? Does it have anything to do with the weights of the gasses. Well yes and no. Technically speaking its all a matter of displacement. How much a balloon can lift could more accurately be modeled mathmaticaly as weight of volume of gas to be displaced subtracted by the weight of balloon. The helium itself is not lifting anything we are simply taking advantage of helium's greater intramolecular repulsion forces to displace the atmosphere.

How high a balloon can go is essentially when it reaches an equilibrium point where the weight of the volume of atmosphere displaced is equal to the weight of the balloon. If a balloon could not expand and could contain the pressure of the gas inside, it would not go as high as a balloon that could expand because it would not be able to displace as much of the atmosphere.

#### Markd77

Joined Sep 7, 2009
2,806
So what causes a balloon to float anyways? Does it have anything to do with the weights of the gasses. Well yes and no. Technically speaking its all a matter of displacement. How much a balloon can lift could more accurately be modeled mathmaticaly as weight of volume of gas to be displaced subtracted by the weight of balloon. The helium itself is not lifting anything we are simply taking advantage of helium's greater intramolecular repulsion forces to displace the atmosphere.
Actually the weight of the gas is the most important thing. A given volume of any gas at a certain pressure and temperature contains roughly the same number of molecules as any other gas (ignoring that real gasses don't perfectly obey the ideal gas laws, but it's close).
Molecules of helium just have less mass than the average of air molecules by a factor of about 7.