Question

what do we mean by density?
a. density is used to describe compactness or crowding
b. density is used to describe how much liquid is in a container.
c. density is used to describe how thick a liquid is.
d. density is used to describe the area on a surface
what do we mean by concentration?
a. concentration is used to describe how hot or cold a substance is.
b. concentration is used to describe how fast a substance is changing in volume.
c. concentration is used to describe the amount of one substance that is mixed with another.
d. concentration is used to describe how thick a liquid is.

Explanation:

Density is a measure of how much mass is contained in a given volume, which can be thought of as compactness or crowding of matter. Concentration refers to the amount of one substance (solute) mixed with another (solvent).

Answer:

A. Density is used to describe compactness or crowding
C. Concentration is used to describe the amount of one substance that is mixed with another