Answer:
Density measures the amount of mass per unit of volume in a substance. Concentration describes the amount of a substance dissolved in another substance. Changing the concentration of a solution changes the density of the solution.
Answer: solid
Explanation: Chemical reactions are those which involve rearrangement of atoms.
Chemical changes are accompanied by following changes:
1) Absorption or release of heat
2) Change in color
3) Formation of gas bubbles
4) Formation of a solid product called as precipitate
Example of formation of precipitate or solid in chemical reaction: