The Language of The Language of ChemistryChemistryThe Language of The Language of ChemistryChemistry

• CHEMICAL ELEMENTSCHEMICAL ELEMENTS - - – pure substances that cannot be decomposed by pure substances that cannot be decomposed by

ordinary means to other substances.ordinary means to other substances.

SodiumBromine

Aluminum

The Language of The Language of ChemistryChemistryThe Language of The Language of ChemistryChemistry

• The elements, The elements, their names, and their names, and symbols are given symbols are given on theon the PERIODIC PERIODIC TABLETABLE

• How many How many elements are elements are there?there?

Copper Copper atoms on atoms on silica silica surface.surface.

See CD-See CD-ROM ROM Screen 1.4Screen 1.4

• An An atomatom is the smallest particle of an is the smallest particle of an element that has the chemical element that has the chemical properties of the element.properties of the element.

Distance across = 1.8 nanometer (1.8 x 10-9 m)

An atom consists of aAn atom consists of a

• nucleusnucleus

–(of (of protonsprotons and and neutronsneutrons) )

• electronselectrons in space about the nucleus. in space about the nucleus.

The The AtomAtom

Electron cloudElectron cloud

NucleusNucleus

The red compound is composed of• nickel (Ni) (silver)• carbon (C) (black)• hydrogen (H) (white)

• oxygen (O) (red)• nitrogen (N) (blue)

The red compound is composed of• nickel (Ni) (silver)• carbon (C) (black)• hydrogen (H) (white)

• oxygen (O) (red)• nitrogen (N) (blue)

CHEMICAL COMPOUNDSCHEMICAL COMPOUNDS are composed of atoms and so can are composed of atoms and so can be decomposed to those atoms.be decomposed to those atoms.

AA MOLECULEMOLECULE is the smallest unit is the smallest unit of a compound that retains the chemical of a compound that retains the chemical characteristics of the compound.characteristics of the compound.Composition of molecules is given by aComposition of molecules is given by a MOLECULAR FORMULAMOLECULAR FORMULA

HH22OO CC88HH1010NN44OO22 - caffeine - caffeine

Chemical Properties and Chemical Properties and Chemical ChangeChemical Change

• Chemical change Chemical change or or chemical reactionchemical reaction — — transformation of one or transformation of one or more atoms or molecules more atoms or molecules into one or more different into one or more different molecules.molecules.

•Burning hydrogen (HBurning hydrogen (H22) in ) in oxygen (Ooxygen (O22) gives H) gives H22O.O.

Evolution heat or light

Color change

Formation of gas

Precipitate

Chemical Change

A A Chemist’s Chemist’s

ViewView

2 H2(g) + O2 (g) --> 2 H2O(g)

MacroscopicMacroscopicMacroscopicMacroscopic

SymbolicSymbolicSymbolicSymbolicMicroscopicMicroscopicMicroscopicMicroscopic

Physical ChangesPhysical ChangesSome Some physical changes physical changes

would bewould be

• boiling of a liquidboiling of a liquid

• melting of a solidmelting of a solid

• dissolving a solid in a dissolving a solid in a liquid to give a liquid to give a homogeneous mixture homogeneous mixture — a SOLUTION.— a SOLUTION.

PhasePhase ChangesChanges

areare Changes inChanges in PositionPosition

andand areare

PhysicalPhysical ChangeChange

2. Chemical Properties

The way a substance reacts with others to form new substances with different properties.

Chemical Properties

FlamabilityReactivitycorrosion

Physical Physical PropertiesProperties

What are some physical What are some physical properties?properties?

• colorcolor

• melting and boiling melting and boiling pointpoint

• odorodor

DENSITYDENSITYDENSITYDENSITY• Density is an Density is an

INTENSIVEINTENSIVE property property of matter.of matter.

–does does NOTNOT depend on depend on quantity of matter.quantity of matter.

– temperaturetemperature

• Contrast with Contrast with EXTENSIVEEXTENSIVE

–depends on quantity depends on quantity of matter.of matter.

–mass and volume.mass and volume.

StyrofoamStyrofoam BrickBrick

DENSITYDENSITY - an important - an important and useful physical propertyand useful physical property

Density mass (g)volume (cm3)

Density mass (g)volume (cm3)

Mercury

13.6 g/cm13.6 g/cm33 21.5 g/cm21.5 g/cm33

Aluminum

2.7 g/cm2.7 g/cm33

Platinum

ProblemProblem A piece of copper has a A piece of copper has a mass of 57.54 g. It is 9.36 cm long, mass of 57.54 g. It is 9.36 cm long, 7.23 cm wide, and 0.95 mm thick. 7.23 cm wide, and 0.95 mm thick. Calculate density (g/cmCalculate density (g/cm33).).

Density mass (g)volume (cm3)

Density mass (g)volume (cm3)

STATES OF MATTERSTATES OF MATTERSTATES OF MATTERSTATES OF MATTER•SOLIDSSOLIDS — have rigid shape, fixed — have rigid shape, fixed

volume. External shape can reflect the volume. External shape can reflect the atomic and molecular arrangement.atomic and molecular arrangement.

–Reasonably well understood.Reasonably well understood.

•LIQUIDSLIQUIDS — have no fixed shape and — have no fixed shape and may not fill a container completely. may not fill a container completely.

–Not well understood.Not well understood.

•GASESGASES — expand to fill their container. — expand to fill their container.

–Good theoretical understanding.Good theoretical understanding.

Temperature ScalesTemperature Scales

Notice that 1 kelvin degree = 1 degree Celsius1 kelvin degree = 1 degree Celsius

Boiling point Boiling point of waterof water

Freezing point Freezing point of waterof water

CelsiusCelsius

100 ˚C100 ˚C

0 ˚C0 ˚C

100˚C100˚C

KelvinKelvin

373 K373 K

273 K273 K

100 K100 K

FahrenheitFahrenheit

32 ˚F32 ˚F

212 ˚F212 ˚F

180˚F180˚F

Calculations Calculations Using Using TemperatureTemperature

• Generally require temp’s in Generally require temp’s in kelvinskelvins

• T (K) = t (˚C) + 273.15T (K) = t (˚C) + 273.15

• Body temp = 37 ˚C + 273 = 310 KBody temp = 37 ˚C + 273 = 310 K

• Liquid nitrogen = -196 ˚C + 273 = 77 KLiquid nitrogen = -196 ˚C + 273 = 77 K

• Generally require temp’s in Generally require temp’s in kelvinskelvins

• T (K) = t (˚C) + 273.15T (K) = t (˚C) + 273.15

• Body temp = 37 ˚C + 273 = 310 KBody temp = 37 ˚C + 273 = 310 K

• Liquid nitrogen = -196 ˚C + 273 = 77 KLiquid nitrogen = -196 ˚C + 273 = 77 K

Kinetic Nature of MatterKinetic Nature of MatterKinetic Nature of MatterKinetic Nature of MatterMatter consists of atoms and molecules Matter consists of atoms and molecules

in motion.in motion.

Pure Substances / Mixtures

Heterogeneous Mixtures

Platinum

Homogeneous