Helium gas is added to a balloon, already partially filled with helium gas, the balloon inflates, because the
1 molecules in the balloon have become larger
2. Molecules are moving faster in the balloon than in the cylinder.
3. Helium molecules are heavier in the balloon than in the cylinder containing the gas.
4. Helium molecules do not collide with each other.
5. Helium molecules exert increased pressure in the balloon.