Passage IV

When 2 aqueous (water-based) solutions are mixed together, a chemical reaction between the substances dissolved in the solutions may take place. Evidence of a chemical reaction includes one or more of the following:

formation of a precipitate (ppt, a solid)

release of heat to the solution (solution gets hotter)

absorption of heat from the solution (solution gets colder)

release of a gas (indicated by the formation of bubbles or by an odor)

The table below shows what was observed when various aqueous solutions were mixed.

Table adapted from J. Dudley et al., Health Chemistry—Teacher's Annotated Edition. ©1987 by D. C. Health and Company.