Step-by-step explanation:
Volume is the space occupied by a substance in a container or vessel.
Temperature is the measure of degree of hotness present in a substance or object.
Density is defined as the mass present in per unit volume of a substance. So, more is the mass of a substance more will be its density.
Also, more is the number of particles present in a substance more will be its mass.
Pressure is defined as the push applied on a substance due to which molecules of a gas will come closer to each other.
Therefore, we can conclude that factors which can be changed for a gas without changing the mass of the gas are volume, temperature, and pressure.