Welcome to the Welcome to the World of World of ChemistryChemistry

Yale University Yale University Chemistry 113

Lectures:Lectures: Prof. Victor S. Batista Prof. Victor S. BatistaDiscussions:Discussions: Dr. Iona Black Dr. Iona Black Ms. Brooke Rosenzweig Ms. Brooke Rosenzweig Mr. Robert Snoeberger Mr. Robert Snoeberger

REGISTRATION

Chem 113 students have to register their preferences for a discussion section online as well as in the hard copy card distributed during the first lecture.

Students will be able to register their section or lab preference (1, 2, 3) online by following instructions at the Online Course Information (OCI) website.

Preference selection has opened and will close on Friday, Sept. 7 at 12:30 PM. At that time each instructor will be able to assign students according to their preferences for sections.

The office staff will upload the section assignments to the Online Course System (OCS) and students will be able to see their section on their course registration sheet.

Where’s the Syllabus ?Where’s the Syllabus ?

https://classesv2.yale.edu/portal/

What does Chemistry concern What does Chemistry concern with ?with ?What does Chemistry concern What does Chemistry concern with ?with ?Chemistry is the foundation of all molecular sciencesChemistry is the foundation of all molecular sciences

Chemistry provides understanding, prediction Chemistry provides understanding, prediction and control of the nature and behavior of and control of the nature and behavior of

mattermatter

Chemistry is practical and profoundly philosophicalChemistry is practical and profoundly philosophical

HOW CAN SUBSTANCES BE MADE ?HOW CAN SUBSTANCES BE MADE ?HOW DOES MATTER REACT ?!HOW DOES MATTER REACT ?!

WHAT MATTER IS ?!!WHAT MATTER IS ?!!

Chemistry & Chemistry & MatterMatter

• Chemistry explores the Chemistry explores the MACROSCOPIC MACROSCOPIC world — what we world — what we can see — can see —

• to understand the to understand the PARTICULATEPARTICULATE world we cannot see. world we cannot see.

EXPERIMENTSEXPERIMENTS provide insights into these worlds beyond provide insights into these worlds beyond what our eyes can actually see!!what our eyes can actually see!!

Chem 113 students are strongly Chem 113 students are strongly encourage to take the lab Chem 116Lencourage to take the lab Chem 116L

Chemistry 116L Fall 2007 

Register in Chem 116L online through the OCS 

Placement list will be available online on September 7. 

Purchase a copy of the lab manual from TYCO (corner of Elm & Broadway), and study the first ten pages.

 Next week we have orientation and Ex. 1. at 1 pm (for both the 12 noon and 1 pm

sections). Everyone should try to attend the orientation on the day they are placed in Chemistry 116L. Wear shoes !

 Any questions? Need additional info? Email Dr. G:

narasimhan.ganapathi@yale.edu

A A Chemist’s Chemist’s View: Exp. View: Exp.

II

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

MacroscopicMacroscopicMacroscopicMacroscopic

SymbolicSymbolicSymbolicSymbolicParticulateParticulateParticulateParticulate

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.

Scientific MethodScientific Method• (1)(1) OBSERVE AND QUESTION OBSERVE AND QUESTION about some aspect of the world.about some aspect of the world.

• (2) (2) POSTULATEPOSTULATE a tentative explanation a tentative explanation (HYPOTHESIS)(HYPOTHESIS) and and

make predictionsmake predictions..

• (3) (3) TESTTEST those predictions against those predictions against

observations of reproducible eventsobservations of reproducible events..

• (4) (4) REPEAT REPEAT steps 2 and 3 until there are no more discrepancies steps 2 and 3 until there are no more discrepancies between predictions and observations.between predictions and observations.

When consistency is obtained, When consistency is obtained, hypotheseshypotheses become become a theorya theory (i.e., a coherent set of (i.e., a coherent set of propositions that explain a wide class of propositions that explain a wide class of

phenomena.phenomena.

Types of Observations and Types of Observations and MeasurementsMeasurements

• We make We make QUALITATIVEQUALITATIVE observations of reactions — observations of reactions — changes in color and physical changes in color and physical state.state.

• We also make We also make QUANTITATIVE QUANTITATIVE MEASUREMENTSMEASUREMENTS, which involve , which involve numbersnumbers..

• Use Use SI unitsSI units — based on the — based on the metric systemmetric system

UNITS OF UNITS OF MEASUREMENTMEASUREMENT

Use Use SI unitsSI units — based on the — based on the metric systemmetric system

Length Length

MassMass

TimeTime

TemperatureTemperature

Meter, mMeter, m

Kilogram, kgKilogram, kg

Seconds, sSeconds, s

Celsius degrees, ˚CCelsius degrees, ˚C kelvins, Kkelvins, K

Units of Units of LengthLength

• 1 kilometer (km) = ? meters (m)1 kilometer (km) = ? meters (m)

• 1 meter (m) = ? centimeters (cm)1 meter (m) = ? centimeters (cm)

• 1 centimeter (cm) = ? millimeter (mm)1 centimeter (cm) = ? millimeter (mm)

• 1 nanometer (nm) = 1.0 x 101 nanometer (nm) = 1.0 x 10-9-9 meter meter

• 1 angstrom (A) = 1.0 x 101 angstrom (A) = 1.0 x 10-10-10 meter meter

O—H distance =O—H distance =9.4 x 109.4 x 10-11 -11 mm9.4 x 109.4 x 10-9 -9 cmcm0.094 nm0.094 nm0.940 A0.940 A

O—H distance =O—H distance =9.4 x 109.4 x 10-11 -11 mm9.4 x 109.4 x 10-9 -9 cmcm0.094 nm0.094 nm0.940 A0.940 A

o

o

Temperature ScalesTemperature Scales• FahrenheitFahrenheit

• CelsiusCelsius

• KelvinKelvin

Anders Celsius1701-1744

Lord Kelvin(William Thomson)1824-1907

Temperature ScalesTemperature Scales

Notice that 1 K degree = 1 degree Celsius1 K 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

TemperatuTemperature Scalesre Scales

100 100 ooF = F = 38 38 ooC C = 311 K= 311 K

oF oC K

38 38 ooC C = (100 = (100 ooF – F – 32 32 ooFF) * ) * 100 100 ooC C / 180 / 180 ooFF311 K 311 K = = 273 K 273 K + + 38 38 ooC C * * 100 K 100 K / / 100 100 ooCC

Conversion Factor: 100 ooCC degrees per 180 ooFF degrees

32 32 ooF = 0 F = 0 ooC = 273 KC = 273 K

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

Physical Physical PropertiesProperties

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

• colorcolor

• melting and boiling melting and boiling pointpoint

• odorodor

Physical properties Physical properties characterize the identity characterize the identity of pure substancesof pure substances

salt

sodium

Physical ChangesPhysical ChangesSome Some physical changes physical changes

would bewould be

• boilingboiling of a liquid of a liquid

• meltingmelting of a solid of a solid

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

Physical changes do not Physical changes do not change the identity of change the identity of

Pure SubstancesPure Substances

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

Physical properties, cont’dPhysical properties, cont’d

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)

StrategyStrategy1. Get dimensions in common units.1. Get dimensions in common units.

2.2. Calculate volume in cubic centimeters. Calculate volume in cubic centimeters.

3. Calculate the density.3. Calculate the density.

SOLUTIONSOLUTION

1. Get dimensions in common units.1. Get dimensions in common units.

2.2. Calculate volume in cubic centimeters. Calculate volume in cubic centimeters.

3. Calculate the density.3. Calculate the density.

0.95 mm • 1cm

10 mm = 0.095 cm

57.54 g

6.4 cm3 = 9.0 g / cm3

(9.36 cm)(7.23 cm)(0.095 cm) = 6.4 cm(9.36 cm)(7.23 cm)(0.095 cm) = 6.4 cm33

Note only 2 significant figures in the answer!Note only 2 significant figures in the answer!

Conversion factor

Significant Figures ??!!!# of digits, starting from the left, with

the first digit different from zero.(‘Trailing’ zeros don’t count)

Significant Figures

57.54 g 4 significant figures7.23 cm 3 significant figures0.95 mm 2 significant figures0.095 cm 2 significant figures (zeros to the left of 9 simply locate the decimal point)600. g 3 significant figure 8000 kg 1 significant figure100 cm/m infinte number of significant figures (defined quantity)

INVERSE PROBLEM: Mercury (Hg) has a INVERSE PROBLEM: Mercury (Hg) has a density of 13.6 g/cmdensity of 13.6 g/cm33. What is the mass . What is the mass of 95 mL of Hg in grams? In pounds?of 95 mL of Hg in grams? In pounds?

INVERSE PROBLEM: Mercury (Hg) has a INVERSE PROBLEM: Mercury (Hg) has a density of 13.6 g/cmdensity of 13.6 g/cm33. What is the mass . What is the mass of 95 mL of Hg in grams? In pounds?of 95 mL of Hg in grams? In pounds?

Solve the problem using Solve the problem using DIMENSIONAL DIMENSIONAL ANALYSIS.ANALYSIS.

StrategyStrategy1.1. Use density to calc. mass (g) from Use density to calc. mass (g) from volume.volume.2.2. Convert mass (g) to mass (lb)Convert mass (g) to mass (lb)

Need to know conversion factorNeed to know conversion factor= 454 g / 1 lb= 454 g / 1 lb

PROBLEM: Mercury (Hg) has a density of PROBLEM: Mercury (Hg) has a density of 13.6 g/cm13.6 g/cm33. What is the mass of 95 mL of Hg?. What is the mass of 95 mL of Hg?PROBLEM: Mercury (Hg) has a density of PROBLEM: Mercury (Hg) has a density of 13.6 g/cm13.6 g/cm33. What is the mass of 95 mL of Hg?. What is the mass of 95 mL of Hg?

First, note that First, note that 1 cm1 cm33 = 1 mL = 1 mL

1.1. Convert volume to massConvert volume to mass

PROBLEM: Mercury (Hg) has a density of 13.6 PROBLEM: Mercury (Hg) has a density of 13.6 g/cmg/cm33. What is the mass of 95 mL of Hg?. What is the mass of 95 mL of Hg?PROBLEM: Mercury (Hg) has a density of 13.6 PROBLEM: Mercury (Hg) has a density of 13.6 g/cmg/cm33. What is the mass of 95 mL of Hg?. What is the mass of 95 mL of Hg?

95 cm3 • 13.6 g

cm3 = 1.3 x 103 g

1.3 x 103 g • 1 lb

454 g = 2.8 lb

2.2. Convert mass (g) to mass (lb)Convert mass (g) to mass (lb)

Inverse Inverse ProblemsProblemsInverse Inverse

ProblemsProblems