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General ChemistryIntroduction: Definitions and Measurements

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*Aspartame – NutraSweet™. 5 times sweeter than sugar.

Chemistry is the study of matter, its properties, as well as its transformations and energy

associated with those transformations.

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Chemistry: A Definition

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Nobody fully knows what it really is. Here’s asmuch as we could surmise:

• Matter is the “stuff” around us

• The “stuff” is made of molecules and atoms

Structure of Matter

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Individual Substances,or Compounds:

• identical molecules

• well-defined set of physical and chemical properties

Mixtures:

• different molecules and other particles

• physical and other properties depend on relative amounts of substances in them

Composition of Matter

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SOLIDfixed volumefixed shape

LIQUIDfixed volume

changing shape

GASchanging volumechanging shape

solid salt crystal

NaCl liquid water molecules

molecules of a gas

Three States of Matter

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Examples of physicalproperties:

Melting pointBoiling pointDensityPlasticityConductivityColor

Examples of chemicalproperties:

CorrosivenessFlammabilityOther types of

reactivity

Properties: physical and chemical

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extensive: depend on the amount of substance presentintensive: independent of the amount of substance present

Examples of physical properties and parameters:Mass, volume - extensiveMelting point - intensiveBoiling point - intensiveDensityPlasticityConductivityColor

Physical properties

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extensive: depend on the amount of substance presentintensive: independent of the amount of substance present

Examples of physical properties and parameters:Mass, volume - extensiveMelting point - intensiveBoiling point - intensiveDensity - intensivePlasticity - intensiveConductivity - intensiveColor - intensive

Physical properties

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physical properties:

Color: bluish pale grey metallicMelting point: 419.53 oC [787.15 oF]

Boiling point: 907 oC [1665 oF]

Density: 7140 kg/m3

Resistivity: 5.9.10-8 W m

some chemical properties:

tarnishes in the air very slowly dissolves in dilute acid reacts violently with sulfur (picture above)

Properties: example

Zinc

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Physics: Potential Energyposition of an object

Kinetic Energymotion of an object

Chemistry:Chemical potential energy:

energy stored in the molecules and is determinedby their structure (example: fossil fuels).

Energy: chemical potential energy

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Dawn of humanity: Trial and Error

Modern Science: Observation → Hypothesis → Experiment → Theory

(“educated” trial/error)

A little bit about the scientific method

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Year 1960, International System of Units, SI units

Measurements

SI Fundamental Units of Measurement

Physical Quantity (Dimension) Unit Name Abbreviation

Mass kilogram kgLength meter mTime second sTemperature kelvin KElectric Current ampere AAmount of substance mole molLuminous intensity candela cd

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LengthSI: 1 meter (m) = 1.094 yard

1 cm = 10-2 m = 0.3937 in1 inch = 2.54 cm

VolumeSI: 1 m3

1 L (liter) = 10-3 m3 = 1 dm3

1 mL = 1 cm3 = 10-3 L = 10-3 dm3

1 L = 1.057 quart1 fluid ounce = 29.57 mL

Measurements Useful in Chemistry

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The volume of an irregularly shaped solid can bedetermined by the volume of water it displaces.

Volume: Practice Exercise

Volume (mL) = volume after - volume before = 21.5 mL - 23.0 mL = 1.5 mL (cm3)

Volume (fl. oz.) =

1 fl. oz = 29.57 mL

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The volume of an irregularly shaped solid can bedetermined by the volume of water it displaces.

Volume: Practice Exercise

Volume (mL) = volume after - volume before = 21.5 mL - 23.0 mL = 1.5 mL (cm3)

Volume (fl. oz.) =

1 fl. oz = 29.57 mL

1 29.57

fl. oz = 1 mL

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The volume of an irregularly shaped solid can bedetermined by the volume of water it displaces.

Volume: Practice Exercise

Volume (mL) = volume after - volume before = 21.5 mL - 23.0 mL = 1.5 mL (cm3)

Volume (fl. oz.) = 1.5 mL × = 0.05 fl oz1 fl oz29.57 ml

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Measurements Useful in Chemistry

MassSI: 1 kilogram (kg) = 2.205 lb

1 gram (g) = 10-3 kg

Density (d) !SI: 1 kg/m3 = g/cm3 = g/mL

density = mass volume

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Measurements Useful in Chemistry

Temperature

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Measurements Useful in Chemistry

Temperature

T ºC = (T ºF - 32) 59

T ºF = T ºC + 32 95

T ºC = T K + 273

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Temperature: Practice Exercise

The highest daytime temperature recorded on Mars is 27 ºC,while the average night time temperature is about -107 ºC.What’s the temperature in Fahrenheit, is it comfortable forhumans?

95

T ºF = T ºC + 32

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Temperature: Practice Exercise

T ºF = ×27ºC + 32 = 81 ºF 95Daytime:

The highest daytime temperature recorded on Mars is 27 ºC,while the average night time temperature is about -107 ºC.What’s the temperature in Fahrenheit, is it comfortable forhumans?

95

T ºF = T ºC + 32

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Temperature: Practice Exercise

T ºF = ×27ºC + 32 = 81 ºF 95

T ºF = ×(-107ºC) + 32 = -161 ºF 95

Daytime:

Night time:

The highest daytime temperature recorded on Mars is 27 ºC,while the average night time temperature is about -107 ºC.What’s the temperature in Fahrenheit, is it comfortable forhumans?

95

T ºF = T ºC + 32

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Time

SI standard unit: second (s)

1 hour = 60 min1 min = 60 s

Measurements Useful in Chemistry

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• All devices have limited sensitivity → uncertainty in measurement

2.84 ± 0.01 g; 82740 ± 5 years

• “we always estimate the rightmost digit”

• significant figures: all figures we record in measurement

2.84 g; 82740 years

Significant Figures/Uncertainty inMeasurement

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0.0009039 m 9.1 × 10-5 s 400 L 400. L 400.0 L

Which Figures Are Significant?

all non-zero digits are significant

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0.0009039 m 9.1 × 10-5 s 400 L 400. L 400.0 L

4 sf

Which Figures Are Significant?

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0.0009039 m 9.1 × 10-5 s 400 L 400. L 400.0 L

4 sf 2 sf

Which Figures Are Significant?

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0.0009039 m 9.1 × 10-5 s 400 L 400. L 400.0 L

4 sf 2 sf 1 sf

Which Figures Are Significant?

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0.0009039 m 9.1 × 10-5 s 400 L 400. L 400.0 L

4 sf 2 sf 1 sf 3 sf

Which Figures Are Significant?

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0.0009039 m 9.1 × 10-5 s 400 L 400. L 400.0 L

4 sf 2 sf 1 sf 3 sf 4 sf

Which Figures Are Significant?

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1. multiplication and division: the answer has the samenumber of sf as the measurement with the fewest sf:

Volume (cm3) = 1.23542 cm × 1.0365 cm × 3 cm = 4 cm3

2. addition and subtraction: the answer has the samenumber of decimal places as the measurement with thefewest number of decimal places.

Volume (mL) = 34.1 ml + 4.943567238956 mL = 39.0 mL

Some Math

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Properties: physical/chemical

States of matter: volume/shape

SI standard units of measurement

Measurements: significant figures/uncertainty

Chapter 1: Overview

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Chapter 1: Overview

mass volumedensity =

T ºC = (T ºF - 32)

T ºF = T ºC + 32 95

59

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Practice ExercisesAccording to the ancient greek legend, Archimedes discovered thedisplacement method of density determination while bathing andused it to find the composition of the king’s crown. If a crownweighing 4 lb 13 oz displaces 186 mL of water, is it made of puregold (d = 19.2 g/cm3)?

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Practice Exercises

mass volumedensity = 1 kg = 1000 g = 2.205 lb; 1 oz = 28.3 g

According to the ancient greek legend, Archimedes discovered thedisplacement method of density determination while bathing andused it to find the composition of the king’s crown. If a crownweighing 4 lb 13 oz displaces 186 mL of water, is it made of puregold (d = 19.2 g/cm3)?

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Practice Exercises

mass volumedensity = 1 kg = 1000 g = 2.205 lb; 1 oz = 28.3 g

mass = 4 lb × 1000 g 2.205 lb + 13 × 28.3 g/oz = 2182 g

(1814.1 g) (367.9 g)

According to the ancient greek legend, Archimedes discovered thedisplacement method of density determination while bathing andused it to find the composition of the king’s crown. If a crownweighing 4 lb 13 oz displaces 186 mL of water, is it made of puregold (d = 19.2 g/cm3)?

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Practice ExercisesAccording to the ancient greek legend, Archimedes discovered thedisplacement method of density determination while bathing andused it to find the composition of the king’s crown. If a crownweighing 4 lb 13 oz displaces 186 mL of water, is it made of puregold (d = 19.2 g/cm3)?

mass volumedensity = 1 kg = 1000 g = 2.205 lb; 1 oz = 28.3 g

mass = 4 lb × 1000 g 2.205 lb + 13 × 28.3 g/oz = 2182 g

d = 2182 g/186 mL = 11.7 g/mL = 11.7 g/cm3

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Practice Exercises

mass volumedensity =

Copper coins actually contain very little copper. If a coin is97.3% zinc (d = 7.14 g/cm3) and 2.7% copper (d = 8.95 g/cm3) bymass, what is its density?

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Practice Exercises

mass volumedensity =

Copper coins actually contain very little copper. If a coin is97.3% zinc (d = 7.14 g/cm3) and 2.7% copper (d = 8.95 g/cm3) bymass, what is its density?

mass (Cu) + mass (Zn) volume (Cu) + volume (Zn)=

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Practice Exercises

mass volumedensity =

Copper coins actually contain very little copper. If a coin is97.3% zinc (d = 7.14 g/cm3) and 2.7% copper (d = 8.95 g/cm3) bymass, what is its density?

mass (Cu) + mass (Zn) volume (Cu) + volume (Zn)=

Volume (Zn) = 0.973 g 7.14 g/cm3 = 0.136 cm3

Volume (Cu) = 0.027 g 8.95 g/cm3 = 0.003 cm3

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Practice Exercises

mass volumedensity =

Copper coins actually contain very little copper. If a coin is97.3% zinc (d = 7.14 g/cm3) and 2.7% copper (d = 8.95 g/cm3) bymass, what is its density?

mass (Cu) + mass (Zn) volume (Cu) + volume (Zn)=

Volume (Zn) = 0.973 g 7.14 g/cm3 = 0.136 cm3

Volume (Cu) = 0.027 g 8.95 g/cm3 = 0.003 cm3

density = 1.000 g 0.139 cm3 = 7.19 g/cm3