Chemical Change: Precipitate Formation Experiment
What conclusion can be drawn from the experiment involving the evaporating dish and lab burner?
A. The substances were pure before they were mixed.
B. The substances are toxic and should be handled with extreme caution.
C. A chemical change occurred, producing a new substance known as a precipitate.
D. The substances have been stored for too long and are no longer good.
Answer:
The correct conclusion from the experiment is: C. A chemical change occurred, producing a new substance known as a precipitate.
During the experiment where a clear liquid is heated in an evaporating dish with a lab burner, the disappearance of the liquid and the formation of a solid white residue resembling salt crystals indicate a chemical change has taken place. This change results in the formation of a new substance called a precipitate.
Precipitates are solid particles that are typically formed when dissolved or suspended chemical particles in liquids agglomerate or synthesize. Precipitates are generally insoluble in the liquid phase and can be separated out as a solid. Precipitation reactions occur when a solid substance is separated from a liquid medium.
Examples of precipitation reactions can be seen in everyday life, such as the formation of carbonate compounds at the bottom of a pot when boiling water or the reaction between lime water and carbon dioxide, producing a sediment. These observations indicate that a chemical change has occurred, resulting in the formation of a precipitate.