# The Naked Scientists Forum

### Author Topic: What experimental effects does altitude have on balloons  (Read 7833 times)

#### jeffreyH

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##### What experimental effects does altitude have on balloons
« on: 12/10/2013 17:23:24 »
If one balloon was inflated at sea level and taken to the top of mount everest and the opposite procedure carried out on a second balloon what would the results be?

#### Kr.I.S

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##### Re: What experimental effects does altitude have on balloons
« Reply #1 on: 12/10/2013 17:49:29 »
Assuming both balloons were both inflated to the same volume:

The first balloon inflated at sea level would expand at the top of mt Everest because the air pressure is higher at sea level than it is at high altitude, the air is not pushing on the outside of the balloon as much as it was at sea level while the pressure inside the balloon remains constant, and so the volume increases.

The second balloon inflated at altitude and brought to sea level would decrease in volume due to increasing air pressure i.e having the opposite effect that the first balloon experienced.

#### jeffreyH

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##### Re: What experimental effects does altitude have on balloons
« Reply #2 on: 13/10/2013 00:01:47 »
Assuming both balloons were both inflated to the same volume:

The first balloon inflated at sea level would expand at the top of mt Everest because the air pressure is higher at sea level than it is at high altitude, the air is not pushing on the outside of the balloon as much as it was at sea level while the pressure inside the balloon remains constant, and so the volume increases.

The second balloon inflated at altitude and brought to sea level would decrease in volume due to increasing air pressure i.e having the opposite effect that the first balloon experienced.

OK. So my next question is would there be a change in the energy of the gas molecules in each balloon and by how much.

#### alancalverd

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##### Re: What experimental effects does altitude have on balloons
« Reply #3 on: 13/10/2013 01:08:01 »
If the initial state is p1V1 and the volume changes isothermally to V2, the energy change is p1V1ln(V2/V1)

#### jeffreyH

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##### Re: What experimental effects does altitude have on balloons
« Reply #4 on: 13/10/2013 01:22:14 »
If the initial state is p1V1 and the volume changes isothermally to V2, the energy change is p1V1ln(V2/V1)

Are you saying here that pressure is invariant??

#### CliffordK

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##### Re: What experimental effects does altitude have on balloons
« Reply #5 on: 13/10/2013 01:55:34 »
PV = nRT

n*R doesn't vary.
Pressure will vary.
Pressure at sea level: 1 ATM (101.3 kPA)
Pressure at Mt. Everest: 33.7 kPa or about 1/3 ATM.

Temperature will also vary depending on your experimental design.  I think the peak of Mt Everest is usually below freezing.  At sea level, it will depend on where you are.

However, it would be easiest to consider the temperature fixed, and just vary the pressure, in which the volume would be about 3x at the peak of Mt. Everest.

For some balloons, the pressure to stretch the balloon may vary with the amount it stretches.

If you do choose to add temperature into your equations, you need to convert it to Kelvin.

OK. So my next question is would there be a change in the energy of the gas molecules in each balloon and by how much.

Hmmm....

Thinking of how a refrigerator works, you fix the "energy" of the system.  Compress (or liquefy) a gas, and the temperature of your sample increases.  Reduce the pressure, and the temperature of your sample decreases.

If you had the pressure/volume/temperature, you could tell if the system was gaining or loosing energy.

#### jeffreyH

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##### Re: What experimental effects does altitude have on balloons
« Reply #6 on: 13/10/2013 02:11:14 »
PV = nRT

n*R doesn't vary.
Pressure will vary.
Pressure at sea level: 1 ATM (101.3 kPA)
Pressure at Mt. Everest: 33.7 kPa or about 1/3 ATM.

Temperature will also vary depending on your experimental design.  I think the peak of Mt Everest is usually below freezing.  At sea level, it will depend on where you are.

However, it would be easiest to consider the temperature fixed, and just vary the pressure, in which the volume would be about 3x at the peak of Mt. Everest.

For some balloons, the pressure to stretch the balloon may vary with the amount it stretches.

If you do choose to add temperature into your equations, you need to convert it to Kelvin.

OK. So my next question is would there be a change in the energy of the gas molecules in each balloon and by how much.

Hmmm....

Thinking of how a refrigerator works, you fix the "energy" of the system.  Compress (or liquefy) a gas, and the temperature of your sample increases.  Reduce the pressure, and the temperature of your sample decreases.

If you had the pressure/volume/temperature, you could tell if the system was gaining or loosing energy.

I would like to plot the relationship but experimental data is going to be very tricky.

#### Bored chemist

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##### Re: What experimental effects does altitude have on balloons
« Reply #7 on: 13/10/2013 10:49:01 »
You might want to look at what units the product PV has.

#### Pmb

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##### Re: What experimental effects does altitude have on balloons
« Reply #8 on: 13/10/2013 10:57:20 »
If one balloon was inflated at sea level and taken to the top of mount everest and the opposite procedure carried out on a second balloon what would the results be?
What do you mean by "What would the results be?" The result would be two balloons each filled with a gas. I can't imagine that this is what you were looking for so it must be something else.

I remind you that you need to take the temperature into account. The temperature at different heights is going to be quite different and that will result in different gas pressures inside the balloon.

You can use the ideal gas law so long as you know that's an approximation. Real gases behave a bit differently. However the ideal gas law works very well under a wide range of situations.
Filling the balloo

#### jeffreyH

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##### Re: What experimental effects does altitude have on balloons
« Reply #9 on: 13/10/2013 11:08:50 »
PV = nRT

n*R doesn't vary.
Pressure will vary.
Pressure at sea level: 1 ATM (101.3 kPA)
Pressure at Mt. Everest: 33.7 kPa or about 1/3 ATM.

Temperature will also vary depending on your experimental design.  I think the peak of Mt Everest is usually below freezing.  At sea level, it will depend on where you are.

However, it would be easiest to consider the temperature fixed, and just vary the pressure, in which the volume would be about 3x at the peak of Mt. Everest.

For some balloons, the pressure to stretch the balloon may vary with the amount it stretches.

If you do choose to add temperature into your equations, you need to convert it to Kelvin.

OK. So my next question is would there be a change in the energy of the gas molecules in each balloon and by how much.

Hmmm....

Thinking of how a refrigerator works, you fix the "energy" of the system.  Compress (or liquefy) a gas, and the temperature of your sample increases.  Reduce the pressure, and the temperature of your sample decreases.

If you had the pressure/volume/temperature, you could tell if the system was gaining or loosing energy.

I think all 3 parameters are necessary which is the problem. I don't think this would work for my purposes. There is too much variability. It needs an idealized set of inputs with a predetermined range for temperature drop.

#### Bored chemist

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##### Re: What experimental effects does altitude have on balloons
« Reply #10 on: 13/10/2013 13:55:43 »
The temperature drop is about 6.5 degrees per 1000 metres of altitude. You can treat it as pretty close to linear for the first 10 or 15 Km or so.

What are the units of PV?

#### Kr.I.S

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##### Re: What experimental effects does altitude have on balloons
« Reply #11 on: 13/10/2013 14:48:38 »
units for pressure 1 Pa= 1Nm^-2 units for volume m^3
so units for pressurevolume would be Nm
That's interesting

#### alancalverd

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##### Re: What experimental effects does altitude have on balloons
« Reply #12 on: 13/10/2013 17:53:37 »

#### Bored chemist

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##### Re: What experimental effects does altitude have on balloons
« Reply #13 on: 13/10/2013 19:13:22 »
units for pressure 1 Pa= 1Nm^-2 units for volume m^3
so units for pressurevolume would be Nm
That's interesting

;D
If the temperature is constant then PV is constant (because n, R and T are constant) so the energy is constant.

#### jeffreyH

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##### Re: What experimental effects does altitude have on balloons
« Reply #14 on: 14/10/2013 05:27:49 »
The temperature drop is about 6.5 degrees per 1000 metres of altitude. You can treat it as pretty close to linear for the first 10 or 15 Km or so.

What are the units of PV?

Are there any tables of temperature v altitude available? The only problem here is thermal variation in the atmosphere.

#### The Naked Scientists Forum

##### Re: What experimental effects does altitude have on balloons
« Reply #14 on: 14/10/2013 05:27:49 »