What is a precipitate?

• A. A gas that forms during a reaction
• B. A solid that forms and settles out of a liquid mixture during a chemical reaction.
• C. A liquid that forms a solid at the bottom of a container
• D. A color change in a solution

Answer: (B)

A precipitate is a solid that forms and separates from a liquid during a chemical reaction. It happens when two dissolved substances react to create an insoluble compound, so the solid particles come out of the solution and settle to the bottom (or remain as a cloudy mix). This is different from a gas forming (which would bubble out) or just a color change without a solid forming. For example, mixing solutions that contain ions which form an insoluble salt will produce a solid that you can see or that settles out of the liquid.