Chapter 1 Introduction to Chemistry

Daniel L. RegerScott R. GoodeDavid W. Ball

www.cengage.com/chemistry/reger

Chapter 1 Introduction to Chemistry

What is Science?

“Natural abilities are like natural plants; they need pruning by study.” – Sir Francis Bacon (1561-1626)

• Definitions• Science: knowledge

• Sir Francis Bacon: “And thus knowledge itself is power”• Modern science, the acquisition of knowledge,

is acquired by experience (experiment)

• Chemistry: the study of matter and its interactions with other matter and with energy.

The Nature of Science and Chemistry

Chemistry and the Natural Sciences

• Scientific method: investigations that are guided by theory and earlier experiments.

• Hypothesis: a possible explanation for an event.

• Law: a statement that summarizes a large number of observations.

• Theory: an explanation of the laws of nature.

The Scientific Method

• Matter: anything that has mass and occupies space.

• Mass: the quantity of matter in an object.• Weight: the force of attraction between

an object and other objects.

Matter

Mass on moon and earth is the same.

Weight on moon and earth is the different.

Mass and Weight

• Property: anything observed or measured about a sample of matter.

• Extensive property: depends on the size of the sample.• mass, volume

• Intensive property: independent of sample size.• density, color, melting or boiling point

Properties of Matter

• Physical properties: can be measured without changing the composition of the sample.• mass, density, color, melting point

• Physical change: a change that occurs without changing the composition of the material.• freezing, melting

Physical Properties and Changes

• Chemical properties: describe the reactivity of a material.• Natural gas burns in air; iron rusts.

• Chemical change: at least part of the material is changed into a different kind of matter.• The digestion of sugar is a chemical

change.

Chemical Properties

Practice

State if the underlined property or changes is intensive or extensive and chemical or physical.

a) The color of mercury is silvery.b) The sample of iron rusts by reaction with oxygen.c) The heat released by burning coal can power a city.d) Water boils at 100°C.e) A new pencil is 10 inches long.

• Substances - a material that is chemically the same throughout.• Two types of substances• Elements cannot be broken into simpler

substances.• Compounds can be broken down into

elements.

Classification of Matter

• Substance: cannot be separated into component parts by physical methods.

• Compound: a substance which can be separated into simpler substances by chemical methods.

• Element: a substance which cannot be separated into simpler substances by chemical methods.

Substances

• Mixture: matter that can be separated into simpler materials by physical methods.• Heterogeneous mixture: composition of the

mixture changes from one part to another.• Homogeneous mixture or solution:

composition of the mixture is uniform throughout.

• Alloy: a solution of a metal and another material (usually another metal).

Mixtures

Classification of Matter

Practice

Identify the following types of matter as elements, compounds, heterogeneous mixtures, or homogeneous mixtures.

a)Sodium chloride

b)Stainless steel

c)Chlorine

d)soil

Measurement

• Most modern science depends on measurements• Parts of a measurement• The object of the measurement• The value of the measurement• The units of the measurement• The reliability of the measurement

• Example “The mass of iron was 4.0501 grams

• All parts MUST be present in an answer for complete credit!!

• Modern chemistry is largely based on experimental measurements. The confidence in measurements involves:• Accuracy: agreement of a measurement

with the true value.• Precision: agreement among repeated

measurements of the same quantity.

Accuracy and Precision

accurate and

precise

precise but not

accurate

accurate but not precise

neither accurate

nor precise



• The number of significant figures is the number of digits from the first non-zero digit through the last reported digit.• The uncertainty is at least ±1 unit in the last

reported digit.• Leading zeros – zeros preceding the first

non-zero digit are NEVER significant. • Trailing zeros – a decimal point is the key.

• No decimal – trailing zeros are NOT significant• Decimal – trailing zeros ARE significant

Significant Figures

• Quantities that are not limited by significant figures:• counted numbers or tallies.• defined numbers.• the power of ten in exponential notation.

Significant Figures

• How many significant figures are present in each of the measured quantities?

• 0.00121062006900.01.00120.001060

Significant Figures

• Since trailing zeros in numbers without a decimal points may be confusing for significant figures use scientific notation.

• 100 1? Or should there have been a decimal?

1 x 102 11.0 x 102 21.00 x 102 3

Significant Figures

•Determine the number of significant figures:

100. 100.030505 437,000125,904,000 4.80 x 10-3

4.800 x 10-3 0.0048

Practice

• The absolute uncertainty can be no smaller than the least accurate number.

• 12.02 - 10.4

1.62 • 1.6 • The answer should have no more

decimal places than the least accurate number.

Uncertainty in Addition and Subtraction

• Answers should have no more significant figures than the least accurate number.

• 3121 x 12 = 37452 = 3.7 x 104

# sig. digits 4 x = =

NOT 37!!!!!!

37000 is questionable

2 2 2

Uncertainty in Multiplication and Division

• Determine accuracy in the same order as the mathematical operations, # of significant digits are in red.

• density = 3.7 g/mL

• Be mindful of what your calculator gives you!!

3

2

2.79 g

8.34 mL - 7.58 mLv

m 2.79 g

0.76mL=

33

3

2

=

Mixed Operations

Rounding

• Be cautious about rounding during multiple steps.• Keep more significant figures than you

need in intermediate steps.• Ex:• 2.5 x 4.50 x 11.25 = ?

• Evaluate each expression to the correct number of significant figures.(a) 4.184 x 100.620 x (25.27 - 24.16)

(b)

(c)

8.925 - 8.904x 100%8.925

9.6 x 100.65

8.321+ 4.026

Practice

Calculate each to the correct number of significant figures .a) 0.1654 + 2.07 - 2.114 b) 8.27 x (4.987 - 4.962)

c)

d)

9.5 + 4.1 + 2.8 + 3.175

4 (4 is exact)

x 100%9.025 - 9.024

9.025

Practice

Quantity Unit Abbreviation

Length meter m

Mass kilogram kg

Time second s

Temperature kelvin K

Amount mole mol

Electric current ampere A

Luminous intensity candela cd

Base Units in the SI

Prefix Abbreviation Meaning

mega- M 106

kilo- k 103

centi- c 10-2

milli- m 10-3

micro- 10-6

nano- n 10-9

pico- p 10-12

Common Prefixes Used With SI Units

1 kilogram

is

equal

to

1000 g.

Prefixes Used With SI Units

• Unit conversion factor: a fraction in which the numerator is a quantity equal or equivalent to the quantity in the denominator, but expressed in different units

• The relationship 1 kg = 1000 g• Generates two unit conversion factors:

1kg

g 1000 and

g 1000

kg 1

Unit Conversion Factors

Unit Conversions

• Lets convert 5.73 g to kg.• Start with what you know!!!• Add conversion factors to cancel units• Units must be same on top & bottom to cancel

g

kgg

1000

173.5

grams on topgrams on bottom

0.00573 kg

Practice

Convert the following:

a)17.43 km to cm

b)165 μg to kg

• Volume is the product of three lengths.• The standard unit of volume is the cubic

meter (m3).100 cm = 1 m(100 cm)3 = (1 m)3

106 cm3 = 1 m3

• Two important non-SI units of volume are the liter and milliliter.1 liter (L) = 1000 mL = 1000 cm3

1 mL = 1 cm3

Conversion Among Derived Units

Volumes can be expressed in different units depending on the size of the object.

1 m3 contains1000 L

1 L contains1000 mL

Volume

• Express a volume of 1.250 L in mL, cm3, and m3

33-36

3

33

m10 1,250cm 10

m 1 L 1.250

cm 1,250L 1cm 1000

L 1.250

mL 1,250L 1mL 1000

L 1.250

Using Unit Conversions

• Density: mass per unit volume

•

• Density, in SI base units, is kg/m3 (kg m-3).

• Most commonly used density units are g/cm3 (g cm-3 or g/mL) for solids and liquids, and g/L for gases.

Vm

d

Density

• The density of Ti is 4.50 g/cm3 or 4.50 g = 1 cm3.

• Calculate the volume of 7.20 g Ti.

Conversions Between Equivalent Units

Ti cm 1.60g 4.50

cm 1 Ti g 7.20 3

3

Units cancel

What we knowAnswer:

√ number√ units√ object√ sig figs

English System

Practice

a) Express 323 milliliters in gallons.

b) Express 3.61 cubic feet in cubic centimeters.

273.15TT

F1.8

C1.0F32TT

F32C1.0

F1.8TT

CK

o

oo

FC

oo

o

CF

0 Kelvin 273 373

-273o Celsius 0o 100o

-460o Fahrenheit 32o 212o

For water

Temperature Conversion Factors

• Express 17.5°C in °F and in K.

Practice

Practice• It has been estimated that 1.0 g of seawater contains 4.0 pg

of Au. The total mass of seawater in the oceans is 1.6x1012 Tg, If all of the gold in the oceans were extracted and spread evenly across the state of Georgia, which has a land area of 58,910 mile2, how tall, in feet, would the pile of Au be?Density of Au is 19.3 g/cm3. 1.0 Tg = 1012g.

Practice• One metal object is a cube with edges of 3.00 cm and a mass

of 140.4 g. A second metal object is a sphere with radius 1.42 cm and a mass of 61.6 g. Are these objects made of the same or different metals? Assume the calculated densities are accurate to 1.00%.

Practice

A 40-lb container of peat moss measures 14 x 20 x 30 in. A 40-lb container of topsoil has a volume fo 1.9 gal. •Calculate the density of both the peat moss and the topsoil.•How many bags of peat moss are needed to cover an area measuring 10 ft x 20 ft x 2 in?

PracticeOn a typical day, a hurricane expends the energy equivalent to the explosion of two thermonuclear weapons. A thermonuclear weapon has the explosive power of 1.0 Mton of nitroglycerin. Nitroglycerin generates 7.3 kJ of explosive power per gram of nitroglycerin. The hurricane’s energy comes from the evaporation of water that requires 2.3 kJ per gram of water evaporated. How many gallons of water does a hurricane evaporate per day?

THINK!!

Homework:OWL: All of the required assignmentsbook: All questions from the end of the chapter are

recommended as practice.