What is the amount of matter in something to its volume, or the amount of matter something has in a certain space?

• A. Mass
• B. Density
• C. Weight
• D. Buoyancy

Answer: (B)

Density is the measure of how much matter is packed into a given space. It’s the ratio of mass to volume, so it answers the question of how much matter there is for each unit of space the object occupies. A substance with high density has a lot of mass in a small volume (think a dense metal), while a substance with low density has less mass in the same volume (think a light material like foam).

To hook it to other terms: mass is the total amount of matter regardless of how big the object appears; weight is the gravitational force on that mass and depends on location; buoyancy is the upward force a fluid exerts on an immersed object, related to how much volume is displaced.

So the idea of “amount of matter in a certain space” is captured by density, since it ties mass to the volume it occupies.