Coach Dave EdingerJ. C. Booth Middle School

Physical Science (8A)

Changes in MatterChanges in Matter

ChemistryChemistry is the is the study of the study of the properties of matter properties of matter and the ways in and the ways in which matter which matter changes.changes.

Changes in Matter (contChanges in Matter (cont……))

A change that alters the form or A change that alters the form or appearance of a substance, but does appearance of a substance, but does not change the material into a new not change the material into a new substance is called a substance is called a physical physical changechange..

A change in matter that produces A change in matter that produces new substances with new and new substances with new and different properties is called a different properties is called a chemical changechemical change..

Changes in Matter (contChanges in Matter (cont……))

The key The key characteristic of a characteristic of a chemical reaction is chemical reaction is the production of the production of new materials that new materials that are chemically are chemically different from the different from the starting materials.starting materials.

A solid that forms from the combination of 2 liquids is called a “precipitate.” It always indicates a chemical reaction has occurred.

A color change almost always indicates a chemical reaction….

Any time something is burned, a chemical reaction is occurring…

Gas production (in the absence of a heat source) is a key indicator that a chemical reaction is taking place.

                               

New and different properties are the mark of a chemical change…

Can you tell the difference between a Can you tell the difference between a chemical and physical change???chemical and physical change???

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Describing Chemical ReactionsDescribing Chemical Reactions

A A chemical equationchemical equation is a quick and is a quick and easy way to display a chemical easy way to display a chemical reaction using symbols.reaction using symbols.

HH2 + O + O22 H H22OO

Describing Chemical ReactionsDescribing Chemical Reactions

HH2 + O + O22 H H22OO

Reactants- Materials present at the beginning of the reaction

Products- New materials formed from the completion of the reaction

Reactants

Product(s)

Describing Chemical ReactionsDescribing Chemical Reactions

The The law of Conservation of Masslaw of Conservation of Mass states that the total amount of states that the total amount of matter in a chemical reaction does matter in a chemical reaction does not change!not change!

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Balancing Chemical EquationsBalancing Chemical Equations

HH2 + O + O22 H H22OO

H= 2 atomsH= 2 atoms H= 2 atomsH= 2 atoms O= 2 atomsO= 2 atoms O= 1 atomO= 1 atom

THIS VIOLATES THE LAW OF THIS VIOLATES THE LAW OF CONSERVATION OF MASS!!!CONSERVATION OF MASS!!!

Balancing Chemical EquationsBalancing Chemical Equations

__ H__ H2 + __O + __O22 __H __H22OO

A Coefficient is the number in front of a chemical formula that tells you how many molecules of each reactant and product are present.

2 2

H= 4

0= 2

H= 4

0= 2

BALANCED!!

Characterizing Chemical Characterizing Chemical ReactionsReactions

A A synthesis synthesis reactionreaction occurs occurs when smaller when smaller molecules molecules combine to form combine to form larger ones (more larger ones (more reactants than reactants than products)products)

12H2O + 12CO2 + light 2C6H12O11 + 7O2

Characterizing Chemical Characterizing Chemical ReactionsReactions

Decomposition Decomposition reactionsreactions occur occur when chemicals when chemicals break down into break down into smaller molecules smaller molecules (more products (more products than reactants).than reactants).

2H2O 2H2 + O2

Characterizing Chemical Characterizing Chemical ReactionsReactions

A A replacement replacement reactionreaction occurs when occurs when portions of molecules portions of molecules switch places with switch places with one another (the one another (the number of products number of products is the same as the is the same as the number of reactants)number of reactants)

CaCl2 + Na2SO4 CaSO4 + 2NaCl

Precipitate

Energy in Chemical ReactionsEnergy in Chemical Reactions

Every chemical Every chemical reaction involves reaction involves a change in a change in energyenergy……some some reactions release reactions release energy and some energy and some absorb energy.absorb energy.

Energy in Chemical ReactionsEnergy in Chemical Reactions

A reaction that releases energy in A reaction that releases energy in the form of heat is called anthe form of heat is called an exothermic reactionexothermic reaction..

2Na + 2H2O 2NaOH + H2

Energy in Chemical ReactionsEnergy in Chemical Reactions

A kind of reaction that absorbs A kind of reaction that absorbs energy is called an energy is called an endothermic endothermic reactionreaction..

Getting Reactions StartedGetting Reactions Started

There is always a There is always a minimum amount minimum amount of energy needed of energy needed to start a chemical to start a chemical reactionreaction……this is this is referred to as the referred to as the ““activation activation energyenergy..””

Rates of Chemical ReactionsRates of Chemical Reactions

Rates of Rates of chemical chemical reactions are reactions are affected byaffected by……..

Rates of Chemical ReactionsRates of Chemical Reactions

ConcentrationConcentration

Rates of Chemical ReactionsRates of Chemical Reactions

Surface areaSurface area

+ =

Rates of Chemical ReactionsRates of Chemical Reactions

temperaturetemperature

Rates of Chemical ReactionsRates of Chemical Reactions

CatalystCatalyst- (a - (a material that material that increases the rate increases the rate of a chemical of a chemical reaction by reaction by lowering the lowering the activation energy)activation energy)

Rates of Chemical ReactionsRates of Chemical Reactions

A A catalystcatalyst is a substance that is a substance that increases the rate of a chemical increases the rate of a chemical reaction without being consumed.reaction without being consumed.

“That’s All Folks!”

More to come…