Chemical ReactionsChemical ReactionsCh.21 Sec.1Ch.21 Sec.1

Chemical ReactionsChemical Reactions

•Occurs with chemical changesOccurs with chemical changes

•Make new substancesMake new substances

•Change in which one or more Change in which one or more substances are converted into substances are converted into new substancesnew substances

Signs of Chemical Signs of Chemical ReactionsReactions

•Change in Change in colorcolor

•Release of Release of light, heat, light, heat, gas, sound, or gas, sound, or smellsmell

Examples of Chemical Examples of Chemical ReactionsReactions

• GrowingGrowing

• RipeningRipening

• DecayingDecaying

• BurningBurning

• RustingRusting

Law of Conservation of Law of Conservation of MassMass

•Mass cannot be created or Mass cannot be created or destroyeddestroyed

•Chemical reactions rearrange Chemical reactions rearrange atoms atoms

•Break bonds, rearrange, and make Break bonds, rearrange, and make new bondsnew bonds

•Energy breaks bondsEnergy breaks bonds

Chemical EquationChemical Equation

•A way to describe a chemical A way to describe a chemical reaction using chemical reaction using chemical formulas and other symbolsformulas and other symbols

•Pg. 635; Table 1 and equationPg. 635; Table 1 and equation

Products & ReactantsProducts & Reactants

•Reactants = Reactants = left side of left side of equation equation (ALWAYS)(ALWAYS)

•Products = Products = right side of right side of equation equation (ALWAYS)(ALWAYS)

Chemical EquationsChemical Equations

•Balanced chemical equation Balanced chemical equation – has – has same number of atoms of each same number of atoms of each element on both sides of the element on both sides of the equationequation

•Satisfies the Law of Conservation Satisfies the Law of Conservation of mass.of mass.

Reaction TypesReaction Types

1.1. SynthesisSynthesis

2.2. DecompositionDecomposition

3.3. Single DisplacementSingle Displacement

4.4. Double DisplacementDouble Displacement

5.5. CombustionCombustion

SynthesisSynthesis

Combines 2 substances to make 1 Combines 2 substances to make 1 compoundcompound

A + B --> ABA + B --> AB

Blue + Red --> PurpleBlue + Red --> Purple

Na + Cl --> NaClNa + Cl --> NaCl

1 Product1 Product

SynthesisSynthesis

DecompositionDecomposition

Takes 1 compound and breaks it Takes 1 compound and breaks it apart into 2 or more substancesapart into 2 or more substances

AB --> A + BAB --> A + B

HH22O --> HO --> H22 + O + O22

Opposite of synthesisOpposite of synthesis

1 Reactant1 Reactant

DecompositionDecomposition

Single-DisplacementSingle-Displacement

1 element swaps places with another 1 element swaps places with another element that is in a compoundelement that is in a compound

XA + B --> XB + AXA + B --> XB + AB and A swapped placesB and A swapped places

** Has 1 compound and 1 element on ** Has 1 compound and 1 element on both sidesboth sides

Ex: CuClEx: CuCl22 + Al --> AlCl + Al --> AlCl33 + Cu + Cu

Single-DisplacementSingle-Displacement

Double - DisplacementDouble - Displacement

2 compounds exchange elements 2 compounds exchange elements with each otherwith each other

AX + BY --> AY + BXAX + BY --> AY + BX

** 2 Compounds on both sides** 2 Compounds on both sides

Ex: NaCl + AgF Ex: NaCl + AgF NaF + AgCl NaF + AgCl

Double - DisplacementDouble - Displacement

CombustionCombustion

Oxygen and another compound Oxygen and another compound BURN to make new productsBURN to make new products

OxygenOxygen is ALWAYS a reactant is ALWAYS a reactant

COCO22 + H + H22O O is ALWAYS a productis ALWAYS a product

Ex: CHEx: CH44 + + OO22 --> --> COCO22 + H + H22OO

What Type of Reaction? What Type of Reaction?

Double Double DisplacementDisplacement

DecompositionDecomposition

Single Single DisplacementDisplacement

SynthesisSynthesis

1.1. HCl + NaOH --> HCl + NaOH --> HH22O + NaClO + NaCl

2.2. NaCl --> Na + NaCl --> Na + ClCl22

3.3. Al + FeAl + Fe22OO33 --> --> AlAl22OO33 + Fe + Fe

4.4. PP44 + O + O22 --> P --> P44OO1010

2 Types Energy 2 Types Energy ReactionsReactions

1.1. EndothermicEndothermic

2.2. ExothermicExothermic

EndothermicEndothermic

• Endo = inEndo = in

• Energy is taken in Energy is taken in (absorbed) with (absorbed) with reactantsreactants

• Drops surrounding Drops surrounding environment temp.environment temp.

• Ex: Photosynthesis Ex: Photosynthesis - takes in sunlight- takes in sunlight

ExothermicExothermic

• Exo = outExo = out

• Energy is released Energy is released or given out with or given out with productsproducts

• Raises surrounding Raises surrounding environmentenvironment’’s s temperaturetemperature

• Ex: hand warmersEx: hand warmers

Exo or Endo?Exo or Endo?

1.1. ExoExo

2.2. ExoExo

3.3. EndoEndo

4.4. ExoExo

1.1. Paper burningPaper burning

2.2. Firecracker Firecracker ExplodingExploding

3.3. Plant making Plant making its own foodits own food

4.4. Electric Electric blanketblanket

Reaction RateReaction Rate

• How fast a reaction is goingHow fast a reaction is going

• Factors on rate:Factors on rate:

1.1. TemperatureTemperature

2.2. Surface AreaSurface Area

3.3. ConcentrationConcentration

4.4. StirringStirring

5.5. CatalystsCatalysts

CatalystsCatalysts• Substance that Substance that

speeds up reaction speeds up reaction without being without being permanently permanently changedchanged

• Ex: Enzymes in Ex: Enzymes in our stomach speed our stomach speed up digestion up digestion (lactose)(lactose)

InhibitorsInhibitors

• Substance used to slow down a Substance used to slow down a chemical reactionchemical reaction

• Ex: Food preservatives (prevent Ex: Food preservatives (prevent spoilage)spoilage)

• Product is not changed just how fast Product is not changed just how fast or slow the rate of production occursor slow the rate of production occurs