2. Section 9-1 Section 9.1 Reactions and Equations Recognize evidence of chemical change. Represent chemical reactions with equations. Balance chemical equations. Chemical reactions are represented by balanced chemical equations.

3. Section 9-1 Chemical Reactions chemical reaction process by which one or more substances are rearranged to form different substances evidence of a chemical reaction – Change in temperature – Change in color – Odor, gas, or bubbles may form

4. Section 9-1 Representing Chemical Reactions Chemists use statements called equations to represent chemical reactions. Reactants starting substances. Products substances formed in the reaction. This table summarizes the symbols used in chemical equations.

5. Section 9-1 Representing Chemical Reactions (cont.) In word equations, aluminum(s) + bromine(l) → aluminum bromide(s) reads as “aluminum and bromine react to produce aluminum bromide”. Skeleton equations use symbols and formulas to represent the reactants and products. Al(s) + Br(l) → AlBr 3 (s) Skeleton equations lack information about how many atoms are involved in the reaction

6. Section 9-1 Representing Chemical Reactions (cont.) chemical equation statement that uses chemical formulas to show the identities and relative amounts of the substances involved in a chemical reaction

7. Section 9-1 Balancing Chemical Equations This figure shows the balanced equation for the reaction between aluminum and bromine.

8. Section 9-1 Balancing Chemical Equations (cont.) subscript number written below a symbol gives the number of atoms found in a formula superscript number written above a symbol gives the oxidation number the number of electrons lost or gained coefficient the number written in front of a reactant or product describing the lowest whole-number ratio of the amounts of all the reactants and products

9. Section 9-1 Balancing Chemical Equations (cont.) The most fundamental law in chemistry is the law of conservation of mass. Balanced equations show this law.

10. Section 9-1 Balancing Chemical Equations (cont.)