Ch 1

Welcome to Chemistry!Welcome to Chemistry!

Michael SpathMichael Spath

Class FormatClass Format

Lectures start promptly at 5:45 and Lectures start promptly at 5:45 and end no later then 6:45end no later then 6:45

I will be available after class for I will be available after class for questionsquestions

I will not read the book to youI will not read the book to you I expect you to have read the I expect you to have read the

material BEFORE classmaterial BEFORE class Follow the guidelines in the syllabusFollow the guidelines in the syllabus

Contacting MeContacting Me

Email: Email: [email protected]@lagcc.cuny.edu I will get back to you within a dayI will get back to you within a day

AbsenceAbsence

All homework, quizzes, and tests are All homework, quizzes, and tests are due as specified on the syllabus due as specified on the syllabus unless you make arrangements with unless you make arrangements with me BEFORE handme BEFORE hand

If you have a fever, sore throat, and If you have a fever, sore throat, and cough (i.e., the flu) DO NOT come to cough (i.e., the flu) DO NOT come to class until your temperature has class until your temperature has been normal for one daybeen normal for one day

Absence (Cont.)Absence (Cont.)

I will make every accommodation to I will make every accommodation to keep you current during your illnesskeep you current during your illness

DO NOT catch the flu more then onceDO NOT catch the flu more then once

Have Fun!Have Fun!

Homework Assignment 1Homework Assignment 1Due 9/21/2009Due 9/21/2009

SHOW ALL WORKSHOW ALL WORK CH1CH1

• 1.12, 1.28, 1.32, 1.40, 1.441.12, 1.28, 1.32, 1.40, 1.44 CH 2CH 2

• 2.18, 2.26, 2.44, 2.60, 2.902.18, 2.26, 2.44, 2.60, 2.90

Chapter 1Chapter 1

Why Chemistry?Why Chemistry? How does Chemistry affect you?How does Chemistry affect you? Think aboutThink about

• Electronics (semi-conductors)Electronics (semi-conductors)• MedicineMedicine• EnergyEnergy

MatterMatter

Mass (NOT weight)Mass (NOT weight) SpaceSpace Three statesThree states

• SolidSolid• LiquidLiquid• GasGas

Types Types

Elements (117 of them)Elements (117 of them)• CAN NOT be CAN NOT be brokenbroken down chemically down chemically• CAN be CAN be combinedcombined to make compounds to make compounds

Compounds Compounds • Made of elementsMade of elements• Can be broken down or rearranged by chemical Can be broken down or rearranged by chemical

meansmeans• Always have the same ratio of elements (law of Always have the same ratio of elements (law of

definite proportions)definite proportions)• Properties of compounds are different then Properties of compounds are different then

those of their constituent elements.those of their constituent elements.

Definite ProportionsDefinite Proportions

Water: 1 Water: 1 Oxygen to 2 Oxygen to 2 HydrogenHydrogen

Ammonia: 1 Ammonia: 1 Nitrogen to 3 Nitrogen to 3 HydrogenHydrogen

MixturesMixtures

Do not have definite proportionsDo not have definite proportions• Coffee – 1 sugar or 2? Milk or cream?Coffee – 1 sugar or 2? Milk or cream?

Can be Homogenous or Can be Homogenous or HeterogeneousHeterogeneous

HomogenousHomogenous – the same everywhere – the same everywhere in the sample (salt water)in the sample (salt water)

HeterogeneousHeterogeneous – varies from point – – varies from point – to – point (M&Ms and mixed nuts)to – point (M&Ms and mixed nuts)

SolutionsSolutions

Homogenous Homogenous Can be either liquid, solid, or gas.Can be either liquid, solid, or gas.

• Soda has a gas dissolved in a liquidSoda has a gas dissolved in a liquid• Metallic alloys (the crystalline ones) are Metallic alloys (the crystalline ones) are

solids “dissolved” in solidssolids “dissolved” in solids

Properties of MatterProperties of Matter

Physical – describe what the substance or Physical – describe what the substance or mixture is like (color, temperature, mixture is like (color, temperature, hardness)hardness)

Chemical – describe how the substance Chemical – describe how the substance reacts with other substances reacts with other substances

Specific to an element or compound. If Specific to an element or compound. If the compound is changed chemically, the the compound is changed chemically, the properties change (burn gasoline and the properties change (burn gasoline and the clear liquid becomes COclear liquid becomes CO22 and water and water

Properties of MatterProperties of Matter

Intensive Properties – do not depend Intensive Properties – do not depend on the amount of material (density, on the amount of material (density, reactivity, conductivity, magnetic reactivity, conductivity, magnetic response) These are what we use to response) These are what we use to identify elements and compoundsidentify elements and compounds

Extensive Properties – based on the Extensive Properties – based on the amount of material (mass, volume, amount of material (mass, volume, length)length)

Separation of MixturesSeparation of Mixtures

Chemical Engineers take 3 different Chemical Engineers take 3 different semester long classes on separation semester long classes on separation processesprocesses

Separation method depends on the Separation method depends on the physical properties of the material physical properties of the material


Solids & Liquids are separated by filtration Solids & Liquids are separated by filtration (sink trap), centrifugation (spin cycle), or (sink trap), centrifugation (spin cycle), or settling.settling.

Solutions are separated by distillation Solutions are separated by distillation • Simple distillation like boiling off water from Simple distillation like boiling off water from

salts or other solidssalts or other solids• Multi-stage distillation for liquid – liquid Multi-stage distillation for liquid – liquid

separation (gasoline, alcohol ala Jim Beam)separation (gasoline, alcohol ala Jim Beam)• Multi-stage means that it’s done over and over, Multi-stage means that it’s done over and over,

each stage getting a little closer to the target.each stage getting a little closer to the target.


Uranium 235 - 238 separation by the Uranium 235 - 238 separation by the US 1940 – 1945 (Manhattan Project)US 1940 – 1945 (Manhattan Project)• Mass spectroscopy – multi stage (push Mass spectroscopy – multi stage (push

ionized gaseous U by a strong magnet ionized gaseous U by a strong magnet the heaver 238 does not go as far as the the heaver 238 does not go as far as the 235) this fed…235) this fed…

• Multi stage gas centrifuges – each one Multi stage gas centrifuges – each one produced a gas that had slightly more produced a gas that had slightly more 235235

Units of MeasurementUnits of Measurement

British (what we use)British (what we use)• Temp – Deg. Fahrenheit or RankinTemp – Deg. Fahrenheit or Rankin• Length – Inches, Feet, MilesLength – Inches, Feet, Miles• Mass – PoundsMass – Pounds• Force – Pounds (they are DIFFERENT and Force – Pounds (they are DIFFERENT and

easy to confuse)easy to confuse)

Units of MeasurementUnits of Measurement

Metric or SI (what everyone else Metric or SI (what everyone else uses)uses)• Temp – Deg. Celsius or KelvinTemp – Deg. Celsius or Kelvin• Length – MetersLength – Meters• Mass – GramsMass – Grams• Force – Newtons (not the fig type)Force – Newtons (not the fig type)

Base vs Derived – Derived units are Base vs Derived – Derived units are calculated from base unitscalculated from base units

Why Rankin and KelvinWhy Rankin and Kelvin

They start at ZEROThey start at ZERO• Celsius starts at -273.15Celsius starts at -273.15ooC, F at -460C, F at -460ooFF• Don’t use degrees with Rankin & KelvinDon’t use degrees with Rankin & Kelvin

If you try to do any thermodynamic If you try to do any thermodynamic calculation in C or F (the gas law calculation in C or F (the gas law problems you will be doing) and you problems you will be doing) and you will get a very wrong answer.will get a very wrong answer.

Units of MeasureUnits of Measure

BaseBase & & DerivedDerived Units Units

BaseBase units are like elements, they units are like elements, they can not be broken down any further.can not be broken down any further.

DerivedDerived units are like molecules, units are like molecules, they are made up of one or more they are made up of one or more base unitsbase units

Units of MeasureUnits of Measure

Base unitsBase units• LengthLength• MassMass• TimeTime• TemperatureTemperature• Charge (electrical)Charge (electrical)

Derived unitsDerived units• Volume (lengthVolume (length33))• Density (mass / Density (mass /

volumevolume• Speed (length / time)Speed (length / time)• Force (mass*length / Force (mass*length /

timetime22))• Pressure Pressure

(force/lenght(force/lenght22))• Current (charge / Current (charge /

timetime

Mass and WeightMass and Weight

Mass is the AMOUNT of something Mass is the AMOUNT of something present in a sample.present in a sample.

Weight is the force gravity exerts on Weight is the force gravity exerts on the sample. F=MAthe sample. F=MA

In space, objects are weightless, NOT In space, objects are weightless, NOT mass less. If two space ships collide, mass less. If two space ships collide, they still break.they still break.

ConversionsConversions

Rules of algebra apply:Rules of algebra apply:• A fraction whose numerator and A fraction whose numerator and

denominator are the same equals onedenominator are the same equals one• Any number times one equals that Any number times one equals that

numbernumber Units of measure ARE includedUnits of measure ARE included Our goal is to make a fraction that Our goal is to make a fraction that

will cancel the unwanted unit and will cancel the unwanted unit and leave the desired one leave the desired one

ConversionsConversions

To make life easier, my classmates To make life easier, my classmates and I would always convert and I would always convert everything to SI units, even if the everything to SI units, even if the problem was given with all British problem was given with all British units and we had to convert our units and we had to convert our answers back to British in the end. answers back to British in the end. The harder the problems get, the The harder the problems get, the more sense it makes to use SI more sense it makes to use SI

Conversion ExampleConversion Example

Convert 2. feet into millimetersConvert 2. feet into millimeters

2. 2. feetfeet * * 12 12 inchesinches * *2.5 2.5 cmcm * * 10 mm10 mm

1 1 footfoot 1 1 inchinch 1 1 cmcm

600 mm600 mm

Conversion Example 2Conversion Example 2

Convert 3. kg to stoneConvert 3. kg to stone

3. 3. kgkg * * 1.6 stone 1.6 stone 4.8 stone 4.8 stone

1 1 kgkg


TemperatureTemperature Absolute Zero is the absence of heat Absolute Zero is the absence of heat

and all atomic and molecular and all atomic and molecular movement stops.movement stops.• -273.15 -273.15 ooCC• -460. -460. ooFF• 0 K0 K• 0 R0 R


ooC= 5/9 (C= 5/9 (ooF-32) F-32) ooF=9/5 F=9/5 ooC+32C+32

Convert 72Convert 72ooF to KelvinF to Kelvin

ooC= 0.56 (72-32) = 22.2 C= 0.56 (72-32) = 22.2 ooCC

K= K= ooC +273.15 = 22.2 C +273.15 = 22.2 =273.15=295.4K=273.15=295.4K


Since both K and R start at 0:Since both K and R start at 0:

K = 5/9 R and R = 9/5 KK = 5/9 R and R = 9/5 K

So the last problem could have went:So the last problem could have went:

7272ooF + 460= 532 RF + 460= 532 R

532R * .56 = 295.6K532R * .56 = 295.6K

(Rounding error – we’ll cover that later)(Rounding error – we’ll cover that later)

Dimensional AnalysisDimensional Analysis

If you think it’s hard, we just did it on If you think it’s hard, we just did it on the past two slides.the past two slides.

It is a great way to check an answerIt is a great way to check an answer• If you know you are looking for a density If you know you are looking for a density

in kg / min kg / m33, the units in your calculation , the units in your calculation need to cancel to kg / mneed to cancel to kg / m33. .

Dimensionless NumbersDimensionless Numbers

Dimensionless numbers are used Dimensionless numbers are used extensively in engineeringextensively in engineering

The are ratios of two derived units that The are ratios of two derived units that relate to the concept at hand (like the relate to the concept at hand (like the ratio of dynamic pressure to shearing ratio of dynamic pressure to shearing stress: the Renyolds number Nstress: the Renyolds number NReRe))

For systems with NFor systems with NRe Re < 2,500 there is < 2,500 there is laminar flow, over 4,000 is turbulent flow, laminar flow, over 4,000 is turbulent flow, and in between is a transition area.and in between is a transition area.

Significant FiguresSignificant Figures

Accuracy vs Precision:Accuracy vs Precision:• Accuracy is shooting the apple off of Accuracy is shooting the apple off of

someone's head three timessomeone's head three times Once hitting the top of the appleOnce hitting the top of the apple Once hitting the left sideOnce hitting the left side Once hitting the bottom and slicing your friends scalpOnce hitting the bottom and slicing your friends scalp

• Precision is missing the apple all three times, Precision is missing the apple all three times, but putting all the arrows between your friends but putting all the arrows between your friends eyeseyes

• Accuracy & Precision is knocking the thing off Accuracy & Precision is knocking the thing off by hitting the center all three timesmby hitting the center all three timesm


When we take a measurement, we When we take a measurement, we can see the gap between two marks can see the gap between two marks and estimate the fraction between and estimate the fraction between those marksthose marks

4.754.751 4 5 62 3


Your answers need to reflect how Your answers need to reflect how accurate they areaccurate they are

Even if your calculator can display 16 Even if your calculator can display 16 digits, unless your working for NASA digits, unless your working for NASA or Lockheed, you don’t need all of or Lockheed, you don’t need all of themthem

AddAdd or or SubtractSubtract – count decimals – count decimals MultiplyMultiply or or DivideDivide – count Sig Figs – count Sig Figs


For For ADDINGADDING or or SUBTRACTINGSUBTRACTING::• The number of digits in the number LEAST The number of digits in the number LEAST

decimal places is the number of Sig Figsdecimal places is the number of Sig Figs 547.9 547.9 4 Sig Figs4 Sig Figs 1.0031.003 4 Sig Figs4 Sig Figs 10,325.10,325. 5 Sig Figs5 Sig Figs 10,32510,325 4 Sig Figs (no decimal point 4 Sig Figs (no decimal point

means the last means the last digit is digit is the estimated the estimated one)one)


Addition:Addition:85.32185.321

++ 67.23567.235139.47139.47292.026292.026

139.47 has the least decimal places 139.47 has the least decimal places and thus is the least precise, so your and thus is the least precise, so your answer can only be that precise. The answer can only be that precise. The answer must be rounded to 292.03answer must be rounded to 292.03


MultiplicationMultiplication & & DivisionDivision::• The number of Sig Figs is equal to the The number of Sig Figs is equal to the

number with the least Sig Figs. number with the least Sig Figs. • Let’s say you measure a rectangle and Let’s say you measure a rectangle and

your measurements are 32.5123 and your measurements are 32.5123 and 10.25 – your least precise number has 4 10.25 – your least precise number has 4 Sig Figs, so your answer can not have Sig Figs, so your answer can not have more that that.more that that.


What is the volume of cylinder where What is the volume of cylinder where you measured the height as 8.5 cm you measured the height as 8.5 cm and the diameter 2.25 cm?and the diameter 2.25 cm?

V=1/4∏dV=1/4∏d22 * h * h

V= 0.25 * 3.14159 * (2.25)V= 0.25 * 3.14159 * (2.25)22 * 8.5 * 8.5

V= 33.7967 – the number of Sig Figs is V= 33.7967 – the number of Sig Figs is 2 (8.5) so the number is rounded to 2 (8.5) so the number is rounded to 3434..

Questions?Questions?

Ch 1

Documents

material mass

british units

matter mass

weight mass

si units

number units of measure

units of measurement

units of measurement