as the flames heat the gases in the balloon the volume of the gases increases at constant pressure the volume of all gases increases with increasing temperatures is this statement a scientific theory or law explain

Let's differentiate first what a theory and a law is. A theory is an attempt explanation of a natural phenomenon. When the theory is approved by a number of scientists, this becomes a law. An example would be the ideal gas law. The equation is: PV=nRT. Since volume and temperature are directly proportional, when T increases, the V must also increase.