Which piece of evidence is an indication that a chemical reaction has occurred?
Responses
melting of a substance
melting of a substance
a change in color of a substance
a change in color of a substance
freezing of a substance
freezing of a substance
boiling of a substance
a change in color of a substance
The correct response is: a change in color of a substance
When a chemical reaction occurs, a change in color is often a clear indication that a new substance has been formed. This change in color can result from the formation of new chemical bonds and the rearrangement of atoms to create different chemical compounds.
The piece of evidence that is an indication that a chemical reaction has occurred is a change in color of a substance. Here's how you can understand this:
Chemical reactions involve the rearrangement of atoms and molecules to form new substances. One of the key characteristics of a chemical reaction is that it leads to the formation of different substances with different properties than the original substances. A change in color is often an observable sign that the chemical composition of a substance has been altered.
To determine if a change in color is due to a chemical reaction, you can perform experiments to confirm it. For example, you can compare the original substance with the resulting substance using techniques like spectroscopy or chemical analysis. These methods allow you to identify any new compounds or changes in the molecular structure that indicate a chemical reaction has taken place.
It's important to note that while the other options listed (melting, freezing, and boiling) are physical changes that a substance undergoes, they do not necessarily indicate a chemical reaction. They are related to changes in the state or phase of a substance (solid to liquid to gas) and can be reversed without altering the fundamental identity of the substance. On the other hand, a change in color typically suggests a chemical change has occurred.