Final answer:
Helium has a lower density than air, allowing balloons filled with it to float due to buoyant force. Mylar is often used to make durable helium-filled balloons.
Step-by-step explanation:
The low density of helium makes blimps and weather balloons float. Helium gas has a density that is significantly less than the density of air, which explains why balloons filled with helium are buoyant. Due to helium's low molar mass of 4.00 g/mol compared to air's average molar mass of about 29 g/mol, helium atoms are able to create a buoyant force strong enough to lift balloons. Buoyant force is crucial to the operation of blimps and weather balloons, as it counteracts the force of gravity and allows them to rise when their tethering lines are released.
Based on Boyle's Law, as a helium-filled balloon rises and atmospheric pressure decreases, it expands until it eventually bursts. High altitude temperatures can affect helium's behavior as well. Furthermore, helium atoms can escape Earth's atmosphere due to their speeds that occasionally exceed Earth's escape velocity. To maintain the buoyancy of helium-filled balloons for longer durations, materials like Mylar are used instead of rubber, minimizing helium effusion through material pores.