Chapter 10 Chemical Reactions

Reactions and Equations Section 10.1 Reactions and Equations

Section 10.1 Objectives Recognize evidence of chemical change Represent chemical reactions with equations

Key Terms Chemical reaction Reactant Product Chemical equations coefficient

Chemical Reactions Atoms of one or more substances are rearranged to form different substances Another name= chemical change Important part of everyday life

Evidence of a Reaction How to tell if a chemical reaction has taken place Temperature change Color change Odor Gas bubbles

Representing Chemical Reactions Reactants: the starting substances Products: resulting or ending substances Arrow: “react to produce” or “yield” Reactant 1 + reactant 2  product 1 + product 2

Symbols used in Equations Table 10.1 on page 278 Why do these symbols mean? (g)  (s) (aq) + (l)

Physical States Must know the state of reactant and products in order to determine if reaction will occur

Types of Equations Three types of equations Word Skeleton Chemical

Word Equations Used to indicate the reactants and products of chemical reactions Uses the actual names of the substances involved Setup: Reactant 1 + Reactant 2  Product 1 Ex: Iron(s) + Chlorine(g)  Iron(III) Chloride(s)

Skeleton Equations Uses chemical formulas to represent the substances unlike the word equation Chemical formulas take the place of the words Iron(s) + Chlorine(g)  Iron(III) Chloride(s) would become: Fe(s) + Cl2(g)  Fe Cl3(s)

Practice Problems Page 279

Chemical Equations Uses chemical formulas like the skeleton Shows matter is conserved during a reaction (Law of Conservation of Mass) Uses identities and relative amounts of the substances involved in a chemical reaction Everything is balanced in a chemical equation

Balancing Chemical Equations Find correct coefficients for chemical formulas Coefficient is usually a whole number 1 is understood- not written

Steps to Balance a Chemical Equation 1: Write the skeleton equation 2: Count the atoms of elements in the reactants 3: Count the atoms of elements in the products 4:Change the coefficients to make both sides of the equation the equal 5:Write the coefficient(s) in the lowest ratio possible 6:Check your work Ex: 2H2(g) + O2(g)  2H2O(g)

Practice Problems Page 282

Homework 7-13 on page 283