CHEMISTRY Jacqueline P. Hancock, B.S.,M.Ed CHEMICAL REACTIONS CHEMISTRY Jacqueline P. Hancock, B.S.,M.Ed

How many atoms?

COUNTING ATOMS WKSHEET

CHEMICAL REACTION One or more substances changes into another substance Reactants Products Reactants yields Products Reactants produces Products Reactants equals Products

CHEMICAL EQUATION Representation of a chemical reaction using formulas Skeleton equation- equation w/o amounts of reactants and products(starting point) Physical states(s-solid, g-gas, l-liquid, aq-dissolved in water Catalysts-speeds up a reaction w/o being consumed(written above the yields sign) heat added elec. – electrical current

Purpose of Balancing Equations?

CONSERVATION OF MASS Dalton’s Atomic Theory Reactants are converted to products by breaking and forming bonds. Atoms are rearranged Mass is conserved Atoms are conserved

Parts of the Chemical Equation

Never change subscripts!!! Recall these numbers were part of the original formation of the ionic or covalent bond forming the substance

You can only add/change Coefficients to balance equations

Counting Atoms in Equations

PRACTICE MgO + H3PO4 Mg3(PO4)2 + H2O

KI K + I2

CH4 + O2 CO2 + H2O

Practice Balancing Equations Practice Balancing Equations 15 minutes(Balancing Act Worksheet) Balancing Chemical Reactions Worksheet (a-n) Progress Reports will be given at the “end” of class

Turn in Assignments

Types of Reactions Combination(Synthesis) Decomposition Single Displacement Double Displacement Combustion

Synthesis Two or more substances combine to form a single new substance Metal + Nonmetal metal cation & nonmetal anion Nonmetal + Nonmetal More than one product possible Transition Metal + Nonmetal

Examples of Synthesis Reactions (m + nm, nm + nm, or tm + nm) 2Mg(s) + O2(g) 2MgO(s) 2K(s) + Cl2(g) 2KCl(s) S(s) + O2(g) SO2(g) Sulfur dioxide 2S(s)+3O2(g) 2SO3(g) Sulfur trioxide Fe(s) + S(s) FeS(s) Iron(II) sulfide 2Fe(s) +3S Fe2S3(s) Iron(III) sulfide

Decomposition Single compound breaks down into two or more simpler products One reactant and two or more products Requires energy (heat, light, or elec.)

Single Displacement Rxns One element replaces a second element in a compound Reactivity decreases down the activity series Reactive metals will replace any metal below it in activity series

A + BC AC+ B

Double Displacement Rxns Exchange of cations between two compounds Generally take place in (aq) solution One of the products formed Precipitate Gas or water

Combustion Rxns Element or compound reacts with oxygen producing heat and light Always involves oxygen as the reactant Often other reactant is hydrocarbon Production of CO2 Soot(C) CO (carbon monoxide)

which it breathes IGNITE

How is the cook stove a real life example of a fire triangle?

Type of Reaction Definition  Equation Synthesis Decomposition Single Replacement Double Replacement Two or more elements or compounds combine to make a more complex substance A + B → AB AB → A + B Compounds break down into simpler substances Occurs when one element replaces another one in a compound AB + C → AC + B Occurs when different atoms in two different compounds trade places AB + CD → AC + BD