Laws and theories Law – a generalization that describes the behavior of nature. i.e. Law of Definite Proportions Theory – an explanation of observations.

Laws and theoriesLaws and theories

Law – a generalization that describes Law – a generalization that describes the behavior of nature.the behavior of nature.

i.e. Law of Definite Proportionsi.e. Law of Definite Proportions

Theory – an explanation of Theory – an explanation of observationsobservations

i.e. Dalton’s atomic theoryi.e. Dalton’s atomic theory

MatterMatter

Anything that has mass and takes up Anything that has mass and takes up spacespace

States of MatterStates of Matter

StateState ShapeShape VolumeVolume CompressiblCompressible?e?

SolidSolid DefiniteDefinite DefiniteDefinite NoNo

LiquidLiquid IndefiniteIndefinite DefiniteDefinite NoNo

GasGas IndefiniteIndefinite IndefinitIndefinitee

yesyes

Physical propertiesPhysical properties A quality which can be determined A quality which can be determined

without changing the identity of the without changing the identity of the materialmaterial Freezing pointFreezing point Boiling pointBoiling point ColorColor OdorOdor HardnessHardness DensityDensity SolubilitySolubility

Extensive PropertiesExtensive Properties Depend on how much (the extent) Depend on how much (the extent)

matter there ismatter there is i.e. length, mass, volumei.e. length, mass, volume

Intensive PropertiesIntensive Properties Do NOT depend on how much matter Do NOT depend on how much matter

there isthere is i.e. temperature, density (m/V)i.e. temperature, density (m/V)

SteelSteel Adding the following elements (besides Adding the following elements (besides

carbon) to iron produces steel with carbon) to iron produces steel with these resulting properties.these resulting properties.  

Cr - adds corrosion resistanceCr - adds corrosion resistance Si - improves machinability and weldabilitySi - improves machinability and weldability V - adds strengthV - adds strength Mo - adds strengthMo - adds strength Ni - changes the microstructure, can improve toughnessNi - changes the microstructure, can improve toughness Nb - improves creep resistance with proper heat Nb - improves creep resistance with proper heat

treatmenttreatment Al - removes oxygen to improve strengthAl - removes oxygen to improve strength B - helps to prevent crackingB - helps to prevent cracking N - can improve strength by forming nitridesN - can improve strength by forming nitrides

Chemical PropertiesChemical Properties

Describe the behavior of a material Describe the behavior of a material in reactions that change its identityin reactions that change its identity CombustibilityCombustibility Reactivity with other substancesReactivity with other substances

General classes of elementsGeneral classes of elements

Metals – have luster (shine)Metals – have luster (shine)are malleable (not brittle)are malleable (not brittle)are ductile (can be drawn into wires)are ductile (can be drawn into wires)conduct heat and electricityconduct heat and electricity

Nonmetals- Nonmetals- poor conductors of heat and poor conductors of heat and electricityelectricity

brittlebrittle Metalloids- Metalloids- have characteristics of metals and have characteristics of metals and

nonmetalsnonmetals

Classes of matterClasses of matter

Matter

Pure substance mixture

element homogeneouscompound heterogeneous

ExamplesExamples

elementselements compoundscompounds homo mixhomo mix hetero hetero mixmix

CarbonCarbon water water airair concreteconcrete IronIron carbon dioxide carbon dioxide salt watersalt water milkmilk GoldGold table salt (NaCl) table salt (NaCl) white goldwhite gold woodwood MercuryMercury aspirin aspirin brassbrass sandsand

SolutionsSolutions

SolutionsSolutions are homogeneous mixtures. are homogeneous mixtures.

A A solutesolute (the dissolved substance) is (the dissolved substance) is put in a solvent (the dissolving put in a solvent (the dissolving substance).substance).

The The solventsolvent is the substance there is is the substance there is more of.more of.

Physical ChangesPhysical Changes

- are those in which the identifying are those in which the identifying properties of a substance are properties of a substance are unchangedunchanged

- Ex. : change of phaseEx. : change of phase

breaking, cuttingbreaking, cutting

dissolvingdissolving

Chemical ChangesChemical Changes

- are those in which different are those in which different substances are formedsubstances are formed

- Ex.: burningEx.: burning

rustingrusting

decaying or spoilingdecaying or spoiling

acid reacting with metalacid reacting with metal

Signs of a chemical changeSigns of a chemical change

Heat gained or lostHeat gained or lost Production of a gasProduction of a gas Formation of a precipitateFormation of a precipitate Color changeColor change

Law of Conservation of MassLaw of Conservation of Mass

During a chemical reaction, the mass During a chemical reaction, the mass of the products always equals the of the products always equals the mass of the reactants. mass of the reactants.

Methods of separating a Methods of separating a mixturemixture

Use the different properties of the Use the different properties of the substances to separate them.substances to separate them.

Sand and iron filingsSand and iron filings Sand and saltSand and salt Sand in waterSand in water Water from salt waterWater from salt water Oil in water (immiscible liquids)Oil in water (immiscible liquids) Mixture of pigments Mixture of pigments

filter

Dissolve salt, evaporate water

Remove iron with magnet

Distill the water

Settle and extract less dense liquid

Paper chromatography

chromatography distillation

Chemical symbolsChemical symbols

First letter is always capitalized.First letter is always capitalized. Second letter, if there is one, is never Second letter, if there is one, is never

capitalized.capitalized. Co and CO are very different!Co and CO are very different! Some elements use the Latin nameSome elements use the Latin name

2O means 2 oxygen atoms2O means 2 oxygen atoms

OO22 means two oxygen atoms are means two oxygen atoms are

chemically bonded together.chemically bonded together.

SubstanceSubstance – a homogeneous material – a homogeneous material consisting of one kind of matterconsisting of one kind of matter

CompoundCompound – a substance that can be – a substance that can be decomposed into simpler substances decomposed into simpler substances by chemical meansby chemical means

ElementElement – substances that cannot be – substances that cannot be further broken down. further broken down.