230 likes | 441 Views
Chemical Reactions. Reactions and Equations. Learning Goals. Recognize evidence of chemical change. Represent chemical reactions with equations. Balance chemical equations. Chemical Reactions.
E N D
Chemical Reactions Reactions and Equations
Learning Goals • Recognizeevidence of chemical change. • Representchemical reactions with equations. • Balancechemical equations.
Chemical Reactions • The process by which one or more substances are rearranged to form different substances is called a chemical reaction.
Chemical Reactions • Evidence that a chemical reaction may have occurred: • Change in temperature • Change in color • Odor • Gas bubbles • Appearance of a solid
Representing Chemical Reactions • Chemists use statements called equations to represent chemical reactions.
Representing Chemical Reactions • Reactantsare the starting substances. • Productsare the substances formed in the reaction. • This table summarizes the symbols used in chemical equations.
Representing Chemical Reactions • In word equations, aluminum(s) + bromine(l) → aluminum bromide(s) reads as “aluminum and bromine react to produce aluminum bromide”.
Representing Chemical Reactions • Skeleton equations use symbols and formulas to represent the reactants and products. Al(s) + Br(l) → AlBr3(s) • Both word and skeleton equations lack information about how many atoms are involved in the reaction.
Representing Chemical Reactions • A chemical equationis a statement that uses chemical formulas to show the identities and relative amounts of the substances involved in a chemical reaction.
Balancing Chemical Equations • This figure shows the balanced equation for the reaction between aluminum and bromine.
Balancing Chemical Equations • A coefficientin a chemical equation is 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.
Balancing Chemical Equations • The most fundamental law in chemistry is the law of conservation of mass. • Balanced equations show this law.