Final answer:
The assertion that if two objects have identical mass, volume, or density, they must be made of the same substance is false. Objects with identical mass or volume can still differ in material, and having the same density is not exclusive to a single substance.
Step-by-step explanation:
The statement that if two objects have the same mass, we can know they are made of the same substance is false. Two objects can have the same mass but be composed of different substances. For instance, a kilogram of feathers and a kilogram of steel both have the same mass but differ greatly in volume and density.
Moreover, the assertion that if two objects have the same volume, we can know they are made of the same substance is also false. Objects with the same volume can be made of different materials and have different masses. For example, a liter of oil and a liter of water have the same volume but different masses and densities.
Lastly, the claim that if two objects have the same density, we can know they are made of the same substance is misleading. While density can be a characteristic property of a substance, it is not exclusive. Different materials can have the same density, and therefore, having the same density does not necessarily mean the objects are composed of the same substance.