Question

If you release a helium balloon, it soars upward and eventually pops. Explain this behavior.

Short answer

The helium balloon soars upward due to the principle of buoyancy, as helium is lighter and less dense than air, resulting in a net upward force. As the balloon rises, it experiences decreasing air pressure and temperature, causing the helium molecules inside to move apart and the balloon's volume to increase. This continuous expansion weakens the balloon, while the decrease in temperature causes the material to contract, adding stress. Eventually, the stress on the material becomes too great, causing the balloon to pop.

Step-by-step solution

Understand the Principle of Buoyancy

Buoyancy is the force that allows objects to float in fluids, such as gases and liquids, and this force is determined by the difference in pressure on the upper and lower surfaces of an object. Archimedes' principle states that an object submerged in a fluid will experience an upward force (buoyant force) equal to the weight of the fluid displaced by the object. In the case of a helium balloon, the fluid is air, and the buoyancy force counters the force of gravity, making the balloon float.

Compare the Densities of Helium and Air

The buoyant force that a helium balloon experiences is determined by the difference in density between helium and air. Helium is a lighter gas compared to air because of its atomic composition, with its density being approximately 0.1664 grams per liter, while air has a density of 1.225 grams per liter at sea level and 20 degrees Celsius temperature. Since helium is less dense than air, it will experience a greater buoyant force, causing the balloon to float and rise.

Discuss the Upward Movement of the Balloon

The difference in density causes the helium balloon to experience a net upward force as the buoyant force exceeds the force of gravity acting upon the balloon. This force imbalance causes the balloon to rise in the atmosphere. As the balloon rises, the air pressure becomes lower, which reduces the opposing buoyant force; however, the upward force continues to dominate, resulting in further ascent of the balloon.

Explain the Expansion of the Balloon and Its Eventual Popping

As the helium balloon rises through the atmosphere, it encounters decreasing air pressure as well as decreasing temperature. The decrease in pressure causes the helium molecules inside the balloon to move apart, making the volume of the helium gas inside the balloon larger. The balloon's material stretches as a result of the expanding helium gas, and the continuous expansion weakens the balloon's structure. Simultaneously, the decrease in temperature causes the balloon's material to contract. The combined effects of continuous expansion and contraction of the balloon's material result in stress on the material, weakening it further. Eventually, the stress becomes too much for the balloon material to handle, causing the balloon to pop.