5.1 Synthesis and Decomposition Reactions

Learning Goals Learn how to identify a chemical change Learn what is a synthesis reaction and how to create a synthesis reactions Learn what is a decomposition reaction and how to create a decomposition reaction

Physical Change A physical change affects the form of a chemical substance, but does not change the chemical composition of that substance.

Chemical Change A chemical change occurs when there is the formation of a new substance, but it is not always easy to tell. Evidence of a chemical change may include one or more of the following: 1)Formation of a gas 2)Formation of a precipitate 3)Change in colour 4)Change in odour 5)Change in temperature 6)Production of light A precipitate is an insoluble solid formed in a chemical reaction.

Chemical vs Physical Change

Classifying Chemical Reactions The new substances, or products, that form during chemical changes will depend on the type of chemical reaction occurring. There are four main types of chemical reactions: 1)Synthesis Reactions 2)Decomposition Reactions 3)Single Displacement Reactions 4)Double Displacement Reactions

Synthesis Reaction In a synthesis reaction, two or more reactants combine to produce a new product. This general equation represents a synthesis reaction: An example of a synthesis reaction: 2H 2 (g) + O 2 (g)  2H 2 O( l ) + thermal energy

Example of Synthesis Reaction

Synthesis Reaction Example: Complete and balance the following synthesis reaction. Na(s) + Cl 2 (g) 

Synthesis Reaction Example: Complete and balance the following synthesis reaction. Ca(s) + N 2 (g) 

Decomposition Reaction In a decomposition reaction, a compound breaks down into two or more simpler compounds or elements. The general equation is: Hint: If you compare this general equation with the one for synthesis reactions, you will see that you can think of decomposition reactions as the opposite of synthesis reactions. An example of a synthesis reaction: H 2 CO 3 (aq)  CO 2 (g) + H 2 O( l )

Example of Decomposition Reaction

Decomposition Reaction Example: Complete and balance the following decomposition reaction. AgCl(s) 

Decomposition Reaction Example: Complete and balance the following decomposition reaction. AuCl 3 (s) 

Homework Textbook: Read Section 5.1 Questions pg 184 # 1 – 2, pg 185 # 1 – 4, and pg 187 # 1 – 2 Formal Lab Report Due Tuesday!