chemical reactions 1 or more substances changed into a new substance or substances

Reactants: substances about to react

Products: new substances produced

Reactants Products

YIELD

Law of Conservation of Massmass can neither be created nor destroyed in a chemical reaction

Indicators of State

(s) or (cr): solid

(l): liquid (aq): aqueous dissolved in water

(g): gas

Writing Balanced Chemical Equations

1.Describe the reaction in words

2.Rewrite using formulas and symbols (Check for diatomic elements!)

3. Check equation for atom balance

4. Choose coefficients that balance the equation

Types of Chemical Reactions

Synthesis: 2 or more substances combine to form another more complex substance

A+B AB

Decomposition: 1 substance breaks down into 2 or more simpler substances

AB A+B

Single Displacement: 1 element replaces another in a compound

A + BC AC + BCu + Ag(NO3) Cu(NO3) + Ag

Double Displacement: 2 ionic compounds in solution

Precipitate Water Gas

AB + CD AD + CB

AgNO3(aq) + NaCl (aq) AgCl (s) + NaNO3 (aq)

Bond Energy

The amount of energy required to put a bond together is equal to the amount it takes to pull them apart.

Bonding to hydrogen atoms together absorbs 436 kj of energy.

When two hydrogen atoms are split how much energy is released?

436 kj

Endothermic Reaction: net absorption of energy

More energy is required to break bonds than to form new ones

Bonds formed have greater potential energy than bonds that were broken

Ex. Ice packs

Exothermic Reaction: net release of energy Less energy is required to break old bonds than to

form new ones Bonds formed have less potential energy than the

bonds that were broken Ex. Hand warmers

Bond Energy and Conservation of Energy Energy released in an exothermic

reaction is NOT CREATED BY THE REACTION! It was stored as potential energy in the

bonds of the reactants In an endothermic reaction the

products store energy as potential energy rather than releasing it as heat.

Activation Energy

Energy that may be needed to start a reation Used to break the bonds in the reactants

Catalyst:

A catalyst can increase the rate of a chemical reaction Decreases the activation energy

Decreases costs making rxn more economical

The human body uses enzymes to catalyze reactions

Exploring ad Catalyst: Lab In A Nutshell

The reaction did not take place until the heated copper was added

The copper was not consumed by the reaction

Regains original color

2Cu + O2 2CUO

CuO + C2H5OH C2H4O + H2O + Cu

Read Catalysts for Food Productionp. 319- 321