yes indeed it can, basically anything with hot particles is lighter than cold particles and explands, this is because the heated particles have a lot more energy and little space so they jump around...
The internal temperature will depend on various factors such as the load on the balloon, it's size, and the ambient air temperature. The loading of the balloon will generally be arranged such that...
Both. Heating and cooling deal with energy gained and lost on a quantum to molecular scale (smaller than an atom up to molecules) where the wavelength in this case infrared or larger decides how...