What indication is most suggestive of a chemical reaction?

Answer 1

A chemical reaction occurs when a chemical substance transforms into another. Typically, during chemical reactions, electrons shift from one substance to another when chemical bonds break and form.

One method that can be used to detect a chemical reaction is by studying the change in temperature of either the chemicals themselves or of the vessel containing the reacting chemicals. For instance, mixing caustic soda (lye) with fat or oil produces an intense and potentially dangerous amount of heat, and ultimately results (assuming the correct proportions are used) in hand soap.

Another method is to document the attributes of the chemical before the reaction (pH level, colour, viscosity, etc.) and after the reaction. This is far more useful when one wishes to later determine the path of the reaction (known as the "reaction equation").

For instance, using what's known as a "Universal Indicator Solution", one can add vinegar (an acid, which has a low pH), which results in a chemical reaction turning the solution red. Then, adding ammonia (a base, which has a high pH) turns the solution blue. Adding more vinegar would lower the pH of the overall solution, turning the solution back toward the red spectrum.

This topic is complex, and the reader is encouraged to view the related Wikipedia link below for more information. As with all work in chemistry, be sure to take the necessary precautions prior to experimenting with chemical reactions!

Answer 2

The most suggestive indication of a chemical reaction is the formation of a precipitate, evolution of a gas, change in color, release of heat, or production of light. These changes signify that new substances are being formed through a chemical transformation.

Answer 3

irreversibility if a chemical change occurs then the newly formed compound cannot be changed back into the original substance