Ch 8 Chemical Equations and Reactions Sec. 1 Describing Chemical Reactions Sec 2 Balancing Chemical Equations Sec 3 Classifying Chemical Reactions Sec 4 Writing Net Ionic Equations

Sec 1 Describing Chemical Reactions List evidence that suggests a chemical reaction has occurred and evidence that proves a chemical reaction has occurred Describe a chemical reaction by using a word equation and a formula equation. Interpret notations in formula equations such as those relating to states of matter or reaction conditions

Chemical Change Changes in energy Release of energy as heat Release of energy as light Production of sound Reduction or increase of temperature Absorption or release of electrical energy(battery)

Chemical Changes Formation of new substances Formation of a gas Formation of a precipitate Changes in color Changes in odor

Chemical Changes Some of the previous examples of evidence for a chemical change are not definite To be certain of a chemical change, chemical analysis must be performed. Checks of Density, melting point, and boiling are examples of how to check for a chemical change.

Chemical Changes Chemical reactions either release or absorb energy. When it is released it can be considered a product When it is absorbed it can be considered a reactant Examples on page 262 In order for reactions to take place, the 2 molecules reacting must come into contact with one another

Chemical Changes Chemical equations represent a chemical reaction with words or symbols. How to write a chemical equation… What do all the symbols mean?

Sec. 2 Balancing Equations Relate the conservation of mass to the rearrangement of atoms in a chemical reaction. Write and interpret a balanced chemical equation for a reaction and relate conservation of mass to the balanced equation.

Reactions Conserve Mass What does the law of conservation of mass state?

Balancing Equations During a chemical reaction, atoms are simply rearranged. Following the law of conservation of mass, there must be an equal number of atoms on the product said as there is the reactant side.

Balancing Equations Identify the reactants and products Count atoms Insert Coefficients (number in front of atoms or molecules in the reaction) Verify your results Practice, trial and error

Sec. 3 Classifying Chem Reactions Identify combustion reactions, write chemical equations that predict products. Identify synthesis reactions, write chemical equations that predict products. Identify decomposition reactions, write chemical equations that predict products. Identify displacement reactions, write chemical equations that predict products. Identify double-displacement reactions, write chemical equations that predict products.

Reaction types Combustion Reactions Reaction of a hydrocarbon and oxygen that produces carbon dioxide and water CH4 + O2  CO2 + H2O

Reaction Types Synthesis Reactions Two or more substances are combined to form one compound. (two reactants forming one product). Mg + O2  MgO

Reaction Types Decomposition Reactions Are the opposite of synthesis, one compound is broken down into 2 or more substances. H2 O  H2 + O2

Reaction Types Displacement Reactions When elements or compounds switch positions in a chemical reaction