Ch 8 Chem Equations and Reactions 8.1 Describing Chemical Reactions Physical Indicators Release heat/light Color change Production of a gas Formation of a precipitate (solid) Odor Law of Conservation of Mass Known facts Correct formula (reactantsproducts) Coefficients show mass same

Word Equations Formula Equations Balanced Equations Reactants and products represented with words Formula Equations Using symbols and formulas for reactants and products Subscripts to have neutral compounds Not balanced yet Balanced Equations Coefficients before formulas to follow law of conservation of mass

Important Symbols for writing chemical equations

Balancing Chemical Equations Coefficients represent relative not absolute amounts of reactants and products Relative masses of reactants and products can be determined from coefficients Reverse reaction has same relative amounts as forward reaction Balancing Chemical Equations Identify names of reactants and products, write word equation Write formula equation for reactants and products Balance using law of conservation of mass Count atoms on both sides to check its balanced

8.2 Types of chemical reactions Synthesis Reaction: 2 or more substances combine to make new compound Oxygen and sulfur Metals and Halogens Oxides

Decomposition Reactions: single compound makes 2+ substances Electrolysis: use electric current Metal Carbonates Metal Hydroxides Metal Chlorates Acids

Single-replacement: 1 element replaces similar element in the compound Metals Hydrogen in water with metal Hydrogen in acid with metal Halogens

Double-displacement: the ions of 2 compounds exchange places in aq soln to form new compounds Form precipitate Form gas Form water

Combustion Reaction: substance combines with oxygen and releases large amount of light/heat

8.3 Activity series of the elements Activity series: organized according to ease element will undergo chemical reaction