Anything that reacts at a very fast rate and creates a lot of resultant material that expands very quickly and as much as possible. Oxy-acetylene and gunpowder can be used in small rockets. The...
Depends of which rocket you are talking about. Fire arrows used gun powder, but they were made to explode. Goddars rocket used liquid oxygen and gasoline. The Saturn V F1 engines used Liquid oxygen...
A simple rocket like you fire on the 4th of July is a solid propellent rocket. It is a tube filled with gunpowder that is attached to a stick. The Chinese invented these rockets back around ~1200 AD.