You have a balloon that contains 1 kg of helium that occupies a volume of 4 m sometime later, the balloon still holds 1 kg of helium, but it now occupies a volume of 2m'. your friend suggests that the helium can be considered an isolated system in this case. can they be correct?

Yes! They can be correct

Explanation:

An isolated system is a system where its total energy and mass stay constant.

In this case, even though the volume changed, the mass remains constant (m = 1 kg), so there is no mass exchange, and we must think that the globe is completely closed.

Now, we don't know exactly what happens with energy, but I can give you an example where the total energy of the globe remains constant.

Imagine that the balloon of volume is at a certain height , under some pressure, . If you lower the balloon to a height , the pressure increases, and from the Boyle's law,

,

, where ,

, just like the case you state, and there was no exchange of mass or energy related to the inner gas of the balloon, so yes, They can be correct.

e) none of the above answers are correct

probably not the "magnets"in the magnet, so to speak, are thought to be electrons orbiting in shells. vurrent loops two sides to the loop