Hydrogen molecules are made up of only one element (hydrogen).
Water molecules, H₂O, are compounds because they are made up of more than one element, hydrogen and oxygen.
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I Did this myself and was right
If you start rubbing the balloon against the hair it causes electrons to move from the hair and since electrons are negatively charged, the balloon acquires a negative charge, while the hair, with its loss of negative charges, now has a net positive charge.