How Does Altitude Affect the Properties of Helium in a Balloon?

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As altitude increases, the pressure and temperature decrease, affecting the properties of helium in a balloon. The density of helium decreases due to the relationship between density, pressure, and temperature. The volume of helium expands as altitude rises, while the number of helium moles remains constant throughout the ascent. The mass of helium decreases as temperature drops, but the pressure inside the balloon remains constant. These principles illustrate the behavior of helium in response to changing altitude conditions.
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Homework Statement


I have a balloon on the ground, where it is 20 degrees celcius, and it has a volume of 5L (it is filled with helium). The pressure at the ground is 1 atmosphere. The balloon itself (without helium) weighs 0.1 kg.

I find the force that makes the balloon go up to be:

F_up = (m_air)*g = 58.96 N

F_down = (m_Helium + m_ballon) * g = 9.13 N

So the balloon will go up.

I can also find the number of Helium-moles from n = m/M, and I find that n = 207 moles.

The Attempt at a Solution


My questions are:

As the balloon goes up, the pressure goes down and so does the temperature. I want to know, which parametres are affected by this?

The density of the helium? Yes, because density is written as "rho" = M*p/(R*T), so this changes.

The volume of the helium? yes, this changes as well.

The number of helium-moles? No, this is constant too.

The mass of the helium? Yes, this gets smaller when the temperature goes down since "rho" = m/V.

The pressure inside the balloon? No, this stays the same.

Can you guys please confirm this?
 
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- the pressure of the balloon is constant also, right?
 

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