Why does heating a gas increase its volume?

As when you increase the temperature, the kinetic energy of molecules increases, hence their velocity also increases. read more

Heating a gas will increase the volume if the volume isn't constrained. If the volume is kept constant the pressure will increase. To a good approximation most gases follow the Ideal Gas equation PV=nRT Increasing the temperature means the PV product must increase. read more

Hence you need to know the specific heat capacity of the materials, and the mass, as well as the initial temperatures. The formula relating pressure, volume, amount of moles and temperature is: $PV = nRT$, where R is the gas constant (which depends on what units you use). read more