What would you use to measure the mass difference between two like objects?

What would you use to measure the mass difference between two like objects? You would use a balance scale.

A balance compares an object with a known mass or compares two objects directly. If two like objects are placed on opposite sides, the side that lowers indicates which object has greater mass. The difference can then be determined using calibrated masses or a precision balance.

Density is not the appropriate answer because it describes how much mass is contained in a given volume. Objects can have different masses while sharing the same density, particularly when they are made of the same material but have different sizes.

A balance is also preferable to a spring scale when the goal is mass comparison. A spring scale measures gravitational force, or weight, while a balance compares masses under the same gravitational conditions. In ordinary laboratory settings, this makes the balance the standard instrument for comparing mass.