Welcome to Chemistry

General Chemistry 1

CHEM 1341

Instructor:

Jeff McVey

2

Introduction

• Chemistry– the study of matter and its properties, the

changes that matter undergoes, and the energy associated with those changes

• Matter– the physical material of the universe;

anything that occupies space and has mass

Section 1.1

How Small is an Atom

Scanning Tunneling Microscope (STM) Image

71.3 Angstrom

Components of Every Atom

Formation of the Elements

10

Introduction

• Chemistry– the study of matter and its properties, the

changes that matter undergoes, and the energy associated with those changes

• Matter– the physical material of the universe;

anything that occupies space and has mass

Section 1.1

11

States of Matter

• Gas– has no fixed volume or shape– conforms to the volume and shape of its

container– compressible

• Liquid – has a fixed volume, but no fixed shape– conforms to the shape of its container

• Solid – has a fixed volume and a fixed shape

Section 1.2

Kinetic Energy

• ki·net·ic (k -n t k, k -)adj.– Of, relating to, or produced by

motion.

• Kinetic Energy is the energy that comes from Motion. The Faster something is moving the higher the kinetic energy.

13

States of MatterSection 1.2

14

Changes in States of Matter

Movie

Section 1.2

15Pure Substance (or Substance)

• Matter that has a fixed composition and distinct properties; pure substances contain only one kind of matter

– elements

– compounds

Section 1.2

16

Classification of Substances

• Elements

– substances that can not be decomposed into simpler substances by chemical means

• Compounds

– composed of two or more elements; can be decomposed by chemical means

Section 1.2

17

Periodic TableSection 1.2

18

Diatomic Molecules

• Elements which exist naturally as a combination of two atoms

– H2, N2, O2, F2, Cl2, Br2, I2

Cl Cl O O

Section 1.2

19

Compounds

Compounds are a combination of two or more elements

Section 1.2

H H

OA molecule of water, H2O, contains two atoms of hydrogenand one atom of

oxygen.

20

Summary

Molecules are structures consisting of two or more atoms that are chemically bound

together and behave as an independent unit.

Section 1.2

21

Examples

• H2

• H2O

• NaCl

• Ar

• C6H12O6

molecule

compound

compound

atom

compound

Section 1.2

22

Properties

• Physical Properties

– those that we can measure without changing the basic identity of the substance

• Chemical Properties

– describes the way a substance may change or react to form another substance

Section 1.3

23

Properties

• Intensive Properties

– characteristics of substances whose values do not depend on the amount of material chosen

• Extensive Properties

– characteristics of substances whose values do depend on the amount of material chosen

Section 1.3

24

Changes in Substances

• Physical Changes

– changes in the physical appearance of a substance but not the basic identity

• Chemical Changes

– changes where a substance is transformed into a chemically different substance

Section 1.3

25

Combinations of Substances

• Mixtures

– combinations of two or more substances in which each substance retains its own chemical identity and its own properties

• homogeneous mixtures

• heterogeneous mixtures

Section 1.3

26

Types of Mixtures

• Homogeneous Mixtures

– characterized by being uniform throughout the sample

• Heterogeneous Mixtures

– characterized by not having the same composition, properties, and appearance throughout

Section 1.3

27

Separating Mixtures

• Methods of Separating Mixtures

– filtration

– distillation

– chromatography

Section 1.3

28

Filtration

Filtration is used to separate

heterogeneous mixtures.

Section 1.3

29

Distillation ApparatusSection 1.3

30

Measurements

• SI Units

Mass kilogram (kg)Length meter (m)Time second (s or sec)Electric Current ampere (A)Temperature Kelvin (K)Luminous Intensity candela (cd)Amount of Substance mole (mol)

Section 1.4

31

Metric System PrefixesSection 1.4

E-Instruction

Which of the following is an extensive property?

A. boiling pointB. volumeC. colorD. densityE. temperature

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E-Instruction

Which of the following is not a homogeneous mixture?

A. hot teaB. salt and waterC. sugar and waterD. sand and waterE. cherry Kool-Aid

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E-Instruction34

Which of the figures represents molecules of a compound?

A B C D

35

Metric conversions

To convert meters to millimeters…

or 1000 mm1 m

1 mm10-3 m

Which unit is larger? Give that unit the 1.

E-Instruction

How many centimeters are in a meter?

A. 1B. 0.01C. 100D. 1000E. 0.001

36

37

Scientific Notation

0.000135

18900000

1.35

Number between 1 and 10

x 10-4

1.89 x 107

Number between 1 and 10

38

Mass

• Mass

– a measure of the amount of material in an object

• Weight

– a measure of the attraction between the sample and a gravitational field

Section 1.4

39

Measurements

• Volume

1 mL = 1 cc = 1 cm3

• Density

Density =volumemass

Section 1.4

40

Understanding DensitySection 1.4

10.0 g

Contains 10 mLof distilled H2O

Contains 10 mLof Hg

136.0 g0.0 g 0.0 g

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Example

A sample of carbon tetrachloride, a liquid once used in dry cleaning, has a mass of 39.75 g and a volume of 25.0 mL. What is its density?

Section 1.4

42

Example

The density of magnesium is 1.74 g/cm3. What is the volume of 275 g of this metal?

Section 1.4

43

Temperature

• A measure of the hotness or coldness of an object

– Fahrenheit

– Celsius

– Kelvin

Section 1.4

44

°F = 95

( °C) + 32

K = °C + 273.15

Conversions

°C = 59

( °F - 32)

Section 1.4

45Comparison of Temperature Scales

100° 100° 180°

Section 1.4

46

Example

Perform the following conversion:

72 °F to °C and K

Section 1.4

47

Numbers

• Exact Numbers

– those numbers whose values are known exactly; obtained by counting or by definition

• Inexact Numbers

– those numbers whose values have some uncertainty; obtained by measurement

Section 1.5

48

Recording Numbers

• Precision

– a measure of how closely individual measurements agree with one another

• Accuracy

– refers to how closely individual measurements agree with the correct or “true” value

Section 1.5

Comparison of Precisionand Accuracy

Good accuracyGood precision

Poor accuracyGood precision

Poor accuracyPoor precision

50

beaker graduated cylinder

buret

Uncertainty in Measurements

47 mL 36.4 mL 20.38 mL

10 1 0.1

There is a sign that says 150,000 gallons/second of water flows over

Niagra Fallshttp://www.youtube.com/watch?v=V1opPtgB6d4&feature=related

The sign also says that 567,810 L/s flows over the falls

• This is a gross misuse of significant figures.

• There is an inherent uncertainty in the initial measurement that implies an approximate flow of 140,000 to 160,000 gal/s or +/- 10,000 gal.

• How can you then convert your original measurement to a number that is plus or minus 10 L which about the volume of your average toilet tank.

Rules for CountingSignificant Figures

• All nonzero digits are significant. (1,5,9,2)

• Zeros between nonzero digits are significant. (5.007)

• Zeros to the left of the first nonzero digit are not significant. (0.00027)

• Zeros that fall both at the end of a number and to the right of the decimal point are significant. (0.00250)

• When a number ends in zeros but contains no decimal point, the zeros may or may not be significant. (5200) 2

E-Instruction

Which of the following numbers has three significant figures?

A. 0.001B. 0.0460C. 100D. 3.0 x 102

E. 7.246

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Significant Figuresand Calculations

• Multiplication/Division

– the result must be reported as having no more significant figures than the measurement with the fewest significant figures (23.40 x 0.560 = 13.1)

• Addition/Subtraction

– the result should be reported to the same number of decimal places as that of the term with the least number of decimal places (23.40 + 0.560 = 23.96)

E-Instruction

Complete the following calculation to the correct number of significant figures:

7.8716.1 – 8.44

56

=

57

Dimensional Analysis

A method of problem solving in which units are carried through all calculations.

Dimensional analysis ensures that the final answer of a calculation has the

desired units.

Section 1.6

58

Example

• How many seconds are there in 18 hours?

• How many kilometers are in 26 miles?(1 mile = 5,280 feet, 1 inch = 2.54 cm)

• How many kg/m3 are in 1.74 g/cm3?

Section 1.6