Maybe I’m just too dense to figure this out….
In: Physics
The actual balloon itself (the piece of rubber that we call a balloon) doesn’t change mass at all in the problem – it simply changes shape.
However, the “system” of the ballon plus the gas inside it does change mass. When it is inflated, the balloon contains helium atoms. Those atoms have mass. When the helium atoms are let out of the balloon, the system loses that mass. So the balloon *system* gets lighter.
That may seem counter intuitive because the inflated ballon *feels* so much “lighter” than the deflated balloon – and it even floats! This is because of a different property called density. Density takes into account the object’s mass AND volume, or how much space it takes up.
The inflated balloon takes up wasaaaaaay more space then the deflated balloon, so though it is heavier by a little, it is still a lot less dense – that is, its mass is spread out over a much bigger space. This makes it feel “lighter” and makes it float in the air (because it’s less dense than the air).
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