A balloon filled with hydrogen gas is released into the atmosphere. As it rises higher and external air pressure decreases, what will most likely happen to the balloon?

Introduction / Context:
Gas-filled balloons provide a practical demonstration of buoyancy, pressure and the behaviour of gases in the atmosphere. Hydrogen and helium balloons are lighter than air and rise when released, but they cannot rise indefinitely. This question asks what typically happens to a hydrogen balloon as it ascends to higher altitudes where air pressure is lower.

Given Data / Assumptions:

• The balloon is filled with hydrogen gas, which is much lighter than air.
• The balloon is made of a flexible material such as rubber or latex.
• The balloon is released near the Earth's surface and allowed to rise freely.
• External air pressure and temperature change with height in the atmosphere.

Concept / Approach:
As the balloon rises, the atmospheric pressure outside decreases. According to the gas laws, if the external pressure drops and the balloon's material is elastic, the gas inside will expand, increasing the volume of the balloon. This expansion stretches the balloon material. At some altitude, the combination of internal gas pressure and reduced external pressure can stretch the balloon beyond its elastic limit, causing it to burst. In practice, many hydrogen or helium balloons released from the ground expand greatly and then burst high in the atmosphere rather than floating forever at some level.

Step-by-Step Solution:
Step 1: At ground level, the balloon is in approximate balance: the elastic material contains the hydrogen gas against the surrounding atmospheric pressure. Step 2: As the balloon rises, ambient air pressure decreases with altitude. Step 3: The hydrogen gas inside responds to the lower external pressure by expanding, increasing the balloon's volume. Step 4: The balloon material stretches more and more as the volume increases, and its wall becomes thinner. Step 5: At some height, the material can no longer withstand the internal pressure, and the balloon bursts, releasing the gas into the surrounding air.

Verification / Alternative check:
Weather balloons provide real-world confirmation of this behaviour. They are often launched partially inflated on the ground so that they have room to expand as they ascend. As they rise to high altitudes with very low external pressure, they can expand to many times their original size before eventually bursting. A simple toy hydrogen or helium balloon behaves similarly, though at lower heights. While there can be a temporary equilibrium level where buoyant force equals weight, the continued expansion of the gas typically stresses the balloon material and leads to bursting rather than permanent floating.

Why Other Options Are Wrong:
It will continue to go upwards without any limit: In reality there is a limit due to decreasing pressure, temperature variations and the mechanical strength of the balloon material; it cannot rise indefinitely.

It will reach a certain height and remain floating there forever: Even if it temporarily reaches a neutral buoyancy level, slow leakage or further expansion will eventually change its behaviour; "forever" is unrealistic.
It will reach a particular height and then start coming down while still intact: This might happen for some heavy or thick balloons if gas leaks out, but for a typical hydrogen-filled balloon with thin elastic walls, expansion leading to bursting is the more accurate description tested at this level.

Common Pitfalls:
Learners sometimes assume that because hydrogen is lighter than air, the balloon must simply rise indefinitely. Others focus only on buoyant force and ignore the effect of changing external pressure on the volume and stress in the balloon material. Remember that both buoyancy and material strength matter: the gas wants to expand as pressure falls, and the balloon can fail mechanically at high altitudes.

Final Answer:
A hydrogen balloon will typically expand and burst after reaching some height in the atmosphere.