A chemical change involves 1 or more substances, called reactants, which can combine or break apart on the molecular level to form an entirely new substance, called the product. There are 2 types of reactions: exothermic reactions and endothermic reactions. Exothermic reactions release more energy than they take in and endothermic reactions take in more energy than they release.
The first reaction here is exothermic
You can tell that a chemical reaction has occurred when:
- Temperature changes - A substance disappears
- The odor of the substance changes - The color of the substance changes
- A flame is produced - A different substance is formed
Amazing chemical reactions! YouTube. N.p., n.d. Web. 12 Jan. 2015. <http://youtu.be/ FofPjj7v414>.
"Evidence of Chemical Change." Launceston College. N.p., n.d. Web. 12 Jan. 2015. <http://www.launc.tased.edu.au/online/sciences/PhysSci/pschem/change/Change5.htm>.