http://www.ck12.org Chapter 3. Chemical Interactions
3.15 Recognizing Chemical Reactions
- Identify potential signs that a chemical reaction has occurred.
Look at the girl’s hair in the photo above. It has obviously changed color. The process in which this occurred
involved chemical reactions. How do you know that chemical reactions have occurred? The change in color is the
most obvious clue.
What’s Your Sign?
A change in color is just one of several potential signs that a chemical reaction has occurred. Other potential signs
include:
- Change in temperature-Heat is released or absorbed during the reaction.
- Production of a gas-Gas bubbles are released during the reaction.
- Production of a solid-A solid settles out of a liquid solution. The solid is called a precipitate.
Examples of Chemical Reactions
Look carefully at theFigures3.25, 3.26, and 3.27. All of the photos demonstrate chemical reactions. For each
photo, identify a sign that one or more chemical reactions have taken place. You can see other examples of chemical
reactions at this URL: http://www.youtube.com/watch?v=gs0j1EZJ1Uc.