Propane and LNG, liquid natural gas are two of the most common. Hydrogen and oxygen used by NASA is also stored as pressurized liquid.
They are added fuel tanks so the aircraft can carry more than the normal amount of fuel ; for example, for longer range, or greater endurance.
The solid would be the basket and balloon, and the tanks holding flammable gas. The liquid is water vapor released by burning the gas. The gases are the fuel in the tank, and the heated air in the balloon that causes it to rise.
Chemical Energy.
chemical energy
In Batteries or converted to hydrogen fuel
liquid
It is stored in two separate tanks. In the shuttle, the external tank(s) hold the two fuels as well as smaller tanks inside the shuttles wings.
Diesel is a fuel that is used in cars and stored in tanks. Gasoline / Petrol is another fuel that is used in cars and stored in tanks.
in the wings
Four tanks stored 270 pounds (120 kg) of mono-methyl hydrazine fuel and nitrogen tetroxide oxidizer. They were pressurized by 1.1 pounds (0.50 kg) of helium stored at 4,150 pounds per square inch (28.6 MPa) in two tanks.
The fuel is usually stored in tanks which are strapped to the sides of the basket.
Fuel is generally stored in tanks built into the wings.
In most modern aircraft they are in the wings.
The oxygen is carried in tanks as a liquid, just as the fuel is.
In water filled tanks on the power station site
Most rockets are powered by a mix of hydrogen and oxygen. The fuel is stored in liquid form in giant tanks. Some rockets are boosted by a solid fuel booster a mixture of aluminium, oxidiser, iron and a polymer to bind all the ingreadients together.
The fuel tanks in almost all aircraft are in the wings. They have always been built that way. The designers feel, from several different angles, that it's the best place to have the fuel tanks - simple as that.