Question 3: Does a hydrogen filled balloon possess any potential energy? Explain. ANSWER Hydrogen is the lightest gas (in fact element). Common air in the atmosphere consists of a number of gases heavier than hydrogen. (It is mostly Nitrogen in the atmosphere). So, the volume of Hydrogen in the balloon is lighter than the same volume of air. When Hydrogen filled balloon is in the air, it feels an up-thrust from the heavier air. So it goes up in the air, doing work against the force of gravity (and sure, against the friction with air molecules). The work against the gravitational force is stored as potential energy in the balloon. So, a Hydrogen filled balloon possesses potential energy.