Final answer:
Mass is a measure of the amount of matter in an object, determined by the number and types of atoms present, and is measured using a balance compared to a standard kilogram. It is different from weight, which varies with the gravitational pull based on location.
Step-by-step explanation:
Mass is a measure of the amount of matter that an object contains and does not depend on its location. It is a fundamental property of an object that gives it inertia, the resistance of an object to changes in its state of motion. Mass depends on the number and types of atoms in an object, rather than the gravitational force acting on it. Thus, the correct answer to what mass is would be: a measure of the amount of matter in an object and it only depends on the number and kind of atoms that compose it. To clarify, mass and weight are different: while mass is the same regardless of where the object is located, weight is a measure of the force of gravity acting on that mass and can change depending on where the object is in the universe. In practice, mass is typically determined using a balance, comparing an object with a standard kilogram.