How is the quantity of matter in an object defined?

The quantity of matter in an object is defined as mass. Mass is a fundamental property of matter that measures how much matter is contained within an object, regardless of its location in the universe. It is often measured in grams or kilograms. Mass is an intrinsic property, which means it does not change based on the object's environment or the gravitational field acting upon it.

Weight, by contrast, is the force exerted on an object due to gravity and depends on both the mass of the object and the acceleration due to gravity at a given location. Therefore, weight is not a direct measure of the quantity of matter. Volume refers to the space an object occupies, which does not directly correspond to the amount of matter contained in that object. Density is the mass per unit volume of a substance and is a derived property that relates mass and volume rather than defining them individually. Thus, mass is the correct term to represent the quantity of matter in an object.