The density will change if the amount of matter in the same volume changes. You can have more matter wihtout changing the density, if the matter occupies more space.
The amount of matter in a given volume is represented by the density of the substance. Density is a measure of mass per unit volume, typically expressed in units like grams per cubic centimeter. By multiplying the volume by the density of the substance, you can calculate the amount of matter present.
The simple answer to this would be no. Density is the mass per volume of a substance so if you were to add either one of these quantities the other would have to rise by a proportional amount and the density would remain constant. However this become untrue when the amount of matter you are dealing with become on the order of a planetary mass. This much matter will produce a gravitational field which will cause pressures to result that will be enough to invoke a phase change in the portions from the center of the mass on outwards. In this case the density will change with the change in phase.
density
The amount of matter can vary depending on factors such as the size of an object, its density, and its composition. Matter can change form through physical or chemical processes, but the total amount of matter in a closed system remains constant due to the law of conservation of mass.
Some properties of matter that do not change include mass, which is the amount of matter in an object, and volume, which is the amount of space that matter occupies. Other intrinsic properties such as density, boiling point, and melting point also remain constant under most conditions.
Volume is extensive because it depends on the amount there is unlike an intensive property such as density because and objects density will never change no matter how much there is of it.
The amount of matter in a given volume of space is its D-E-N-S-I-T-Y Its Density NOT Volume!
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Density, I think