4.2 Classifying Chemical Changes and Predicting Products Text pages There are six (6) major categories to classify most chemical reactions 1. Synthesis Reaction Usually release thermal energy so reactions are called exothermic Examples:

4.2 Classifying Chemical Changes and Predicting Products 2. Decomposition Reaction Usually take in thermal energy so reactions are called endothermic Examples:

4.2 Classifying Chemical Changes and Predicting Products 3. Combustion Reaction Release significant amounts of thermal energy in the form of heat and sometimes light and sound. Example Combustion of gasoline

4.2 Classifying Chemical Changes and Predicting Products 4. Single Replacement Reaction During a single replacement reaction, a free, uncombined element “kicks out” a combined element and takes its place. It is important to remember that a metal element always bonds with a non-metal element. Hence metals replace metals, while non-metals replace non-metals. Examples

4.2 Classifying Chemical Changes and Predicting Products Determining Chemical Reactivity or Will the Single Replacement Reaction Occur? *Must consider chemical reactivity A more reactive element will displace Another element in the reaction The higher up in the activity series the more reactive the element What other factors must be considered?

4.2 Classifying Chemical Changes and Predicting Products 5. Double Replacement Reaction Remember positively charged ions are called cations and negatively charged ions are anions. In reactions when these ions trade positions and new compounds are formed the charges must balance as well. There are three categories of double replacement reactions: PrecipitationNeutralizationGas formation Example Other Considerations – What other points need to be remembers with double replacement reactions?

4.2 Classifying Chemical Changes and Predicting Products 6. Neutralization Reaction A salt is composed of the cation from the base and the anion from the acid. Example