Everytime I walk by the balloon stall, I know that they use helium to make the balloons float in the air. But my problem is why when I leave the balloon aside, the balloon sinks to the bottom. Is there anything happen to the helium inside?

  • 1
    $\begingroup$ some of the helium leaks out $\endgroup$ – DavePhD Dec 2 '14 at 13:32
  • 2
    $\begingroup$ maybe I don't understand your question properly, but helium can slowly pass through the wall of the balloon (depending upon the material used), or through an imperfectly sealed closure such as a knot. $\endgroup$ – DavePhD Dec 2 '14 at 13:37
  • $\begingroup$ Maybe the wall. $\endgroup$ – Simon-Nail-It Dec 2 '14 at 13:40
  • $\begingroup$ see: karaloon.com/en/home/quality-and-safety/… $\endgroup$ – DavePhD Dec 2 '14 at 13:40
  • 2
    $\begingroup$ Helium gas is made from tiny atoms which effuse through the pores in the balloon, usually rubber has more pores than a foil balloon so will sink faster $\endgroup$ – theo Dec 2 '14 at 13:45

When the balloon is fully inflated with helium its density (mass/volume) is less than that of the air around it, allowing it to float. Over time, some of the helium will "leak" out of the balloon. As the helium is released the mass of the balloon decreases slightly, but the volume decreases at a much faster rate, resulting in a balloon with a density greater than that of the air around it, which is why it falls to the ground.


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.