ch01

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Chapter 1:Fundamental Concepts and Units of Measurement

Brady & Senese 5th Ed

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Index

1.1. Chemistry is important for anyone studying the sciences

1.2. The scientific method helps us build models of nature

1.3 Matter is composed of elements, compounds, and mixtures

1.4. Properties of matter can be classified in different ways

1.5 Measurements are essential to describe properties

1.6. Measurements always contain some uncertainty

1.7. Units can be converted using the factor-label method

1.8. Density is a useful intensive property

1.1. Chemistry is important for anyone studying the sciences 3

Chemistry and the Sciences

• Chemistry- the study of the composition of matter and its transformations

• Matter- anything that takes up space and has mass• Chemical reaction- change that results from the

interaction of matter.

1.2. The scientific method helps us build models of nature 4

Scientific Method : Getting Started

Observe a Phenomenon-accurately describe something we see, taste, feel,

smell or hear

Pose A Question To Explain The Phenomenon

Form a Hypothesis-a tentative explanation of

the phenomenon


Scientific Method: Testing the Hypothesis

Experiment to Prove or Disprove Hypothesis

If experiment proves hypothesis,

form theory (theoretical model)

If experiment disproves hypothesis,

Pose new question or hypothesis

Continue experimentation. If results form pattern,

considered a law


Scientific Method Case Study: The Process of Growth

• A child sees that a seed, when planted in soil, watered, and exposed to sunlight, grows to form a flower. He concludes that all living things require sunlight, water, and burial in soil to grow.

• Build a case for rebuttal using the scientific method.


Your Turn!

Which of the following is not a hypothesis for the observed plant growth?A. soil is necessary to all growth

B. light is essential to growth of the seed

C. water is required to allow growth

D. plants grow to a greater height if they receive fertilizer

E. none of the above


Your Turn!

A chicken egg is buried, left in the sun, and watered. A second egg is left above the soil, watered and left in the sun. Would this prove that soil is necessary to growth?

A. Yes

B. No


The Scientific Method- Evaluating The Data

A theory is an explanation (based on well-tested, internally consistent experimental results) about why the phenomenon may occur it should explain currently available data It should be as simple as possible It should clearly show underlying connections It should accurately predict future behaviors


The Scientific Method is Cyclical


Atomic Theory Helps Us Visualize Matter

• Air inflates a balloon air must be composed of matter the matter is colliding with the walls

of the container.

• A leaf floats on water’s surface water is composed of particles that

occupy space

• A leaf falls through air, but rests on water’s surface particles are closer in liquid than in

gases


Models Helps Us Visualize Matter

1.3. Matter is Composed of Elements, Compounds, and Mixtures 13

Changes in Matter

• Chemical change- a process that results in the formation of a new substance

• Evidence? Formation of a new solid, new liquid, new gas, temperature change, or an unexpected color change

• Physical change- a process that results in no new substance, but that may change the state of those present, or the proportions


Learning Check: Chemical Or Physical Change?

Chemical Physical

Magnesium burns when heated in a flame

Magnesium metal tarnishes in air

Magnesium metal melts at 922K

Grape Kool-aid lightens when water is added


Your Turn!

Which of the following is not a chemical change?A. a match burns in air

B. ice melts in air

C. an aluminum door whitens in air

D. all of these

E. none of these


• Matter is either a pure substance or a mixture• Mixtures may be separated using physical methods

such as chromatography, filtration, sieving

Matter Can Be Classified By Its Properties:


What Is An Element?

• Elements - substances that cannot be decomposed into simpler substances

• shown on the periodic table as symbols: “K” for potassium and “Na” for sodium

• made of identical atoms, either singly or in groups


Weird Science

• Eleven symbols bear no resemblance to their English names - their names are derived from other languages

• Some of these are used in naming, and these are highlighted

Sb antimony stibium K potassium kalium

Cu copper cuprum Sn tin stannum

Au Gold aurum Na sodium natrium

Ag silver argentum W tungsten wolfram

Fe iron ferrum Hg mercury hydragyrum

Pb lead plumbum


What Is A Compound?

• Compounds - formed from two or more atoms of different elements combined in a fixed proportion

• Have different characteristics than the elements that compose them

• Can be broken down into elements by some chemical changes


Mixtures

• mixtures consist of varying amounts of two or more elements or compounds

• Homogeneous mixtures or “solutions”- have the same properties throughout the sample Brass, tap water

• Heterogeneous mixtures- consist of two or more phases Salad dressing, Coca-Cola ™


Learning Check: Classification

Sand Ice

(H2O)

Flour Table Salt (NaCl)

Pure

Element

Compound

Molecule

Heterogeneous Mix

Homogeneous Mix


Your Turn!

• brass is pure

• natural peanut butter made only by crushing peanuts is pure

• because blood cells can be distinguished from plasma under a microscope, blood is a heterogeneous mixture:

• True• False

• True• False

• True• False

1.4. Properties of matter can be classified in different ways 23

Classification Of Matter By State

Classification by state is based on packing, motion, and shape Solids have fixed shape and volume Liquids have fixed volume, but take the container shape Gases have to expand to fill the shape and volume of

the container


Properties Of Matter

• Chemical properties describe the behavior of the matter that leads to the formation of a new substance: the "reactivity" of the substance

• Physical properties can be observed about the matter alone, without changing the composition


Learning Check: Chemical or Physical Property?

Chemical Physical

Magnesium metal is grey

Magnesium metal tarnishes in air

Magnesium metal melts at 922K

Magnesium reacts violently with hydrochloric acid


Your Turn!

Which of the following is a chemical property?

A. water is colorless

B. water reacts violently with solid Na metal

C. water dissolves table salt

D. all of these

E. none of these


Intensive And Extensive Properties

• Intensive properties are independent of sample size Examples: color, texture and temperature

• Extensive properties depend on sample size Examples: volume and mass

• Properties used to identify substances are always intensive Density, color, and texture are often helpful in

identification, but temperature is not

1.5 Measurements are essential to describe properties 28

Measurements are Observations

• Qualitative observations are non-numerical-- ask “what” or “how” or “why”

• Quantitative observations are numerical--ask “how much” and are also called measurements

• This course is general chemistry with quantitative analysis


Your turn!

Which of the following is a quantitative observation?

A. the height of the plant

B. the mass of water added

C. the temperature of the day

D. all of the above

E. none of the above


• Always involve a comparison

• Require units

• Involve numbers that are inexact (estimated). This uncertainty is due to the limitations of the observer and the instruments used

• In science, all digits in a measurement up to and including the first estimated digit are recorded

Measurements:


Measurements and units

• In the U.S., we use the Imperial (USCS) System

• The scientific community (and most of the world) uses the metric system

• Variations in the metric system exist, thus a standard system is used: International System of Units (SI)

• SI units we will use now: Length (m) Mass (kg) Time (s) Temperature

(K)


Measurement Formula SI UnitsArea length × width m2

Volume length × width × height m3 Velocity distance/time m/sAcceleration velocity/time m/s2 Density mass/volume kg/m3

Derived units

involve a combination of base units, including:


Decimal multipliers

Prefix (Symbol) = Numerical Equivalent• Giga ( G ) = 109

• Mega- ( M ) = 106

• kilo- ( k ) = 103

• centi- ( c ) = 10-2

• milli- ( m ) = 10-3

• micro- ( μ) = 10-6

• nano- ( n ) = 10-9

• pico ( p ) = 10-12


Learning Check: Complete The Missing Information

kg

10-12 g

nm

106 g

cL

109 Hz

10-9 m

10-2 L

pg

Mg

GHz

103 g


Your Turn!

Identify the correct conversion:

A. Gm=109 m

B. 109 Gm = m

C. Gm = 10-9 m

D. none are correct


You May Encounter Non-SI Metric Units:

measurement name symbol Value

length angstrom Å 10-10m

mass amu

metric ton

u

t

1.66054×10-27 kg

103 kg

time minute

hour

min

h

60 s

3600 s

volume liter L 1000 cm3


Mass- Matter Content

USCS: oz (avdp.), lb, T

Metric: g

SI: kg


Length

USCS: in, ft, yd, mi

Metric: L, cm3

SI: m


Volume-bulk

• measured directly, using equipment for volumetric measure

• calculated using dimensional (length) information and appropriate formulas. 1 cm3= 1mL

• USCS: fl. oz., pt., qt., gal

• Metric: L, cm3

• SI: m3


Your Turn!

Which of the following is not a USCS unit?

A. ft.

B. m

C. gal.

D. T.


Your Turn!

Which of the following is not a volume unit?

A. mL

B. qt

C. in3

D. cm


Temperature

• USCS: °F• Metric: °C• SI: K


Temperature Conversions

C 1 K1

C15.273CK tT

F32C5F9

CF

tt


Complete The Following:

• 13.5°C=? °F

• 27.50 °F =? °C

• -34.5 °F =?K

F

FCC

FF

t

3.56323.24

325.135

9

CC

tF

CF

Ct

F

CFFt

Ct

C

FFFt

FC

tC

FFt

50.29

5

1

3250.27

9

5

1

32

5

932

325

9

KC

tK

T

CC

tF

CF

Ct

F

CFFt

2.23615.273

449.369

5

1

325.34

9

5

1

32


Your Turn!

Which of the following is the lowest temperature?

A. 300. K

B. 16 ºC

C. 55 ºF

D. they are the same

1.6. Measurements always contain some uncertainty 46

• Because each measurement involves an estimate, measurements always have error.

• Record all measured numbers, including the first estimated digit

• These digits are called significant digits or significant figures

• Exact numbers have infinite significant digits

Measurement Error


Significant Digits In A Measurement Are Limited By Instrument Precision

• Using the first thermometer, the temperature is 21.3 ºC (3 significant digits)

• Using the more precise (second) thermometer, the temperature is 21.32 ºC (4 significant digits)


• Errors-inherent error due to the equipment or procedure Changing volume due to thermal expansion or contraction

(temperature changes) Improperly calibrated equipment procedural design allows variable measurements

• Mistakes-blunders that you know that you have made. Do not use these data Spillage Incomplete procedures Reading scales incorrectly Using the measuring device incorrectly

Errors Arise From A Number Of Sources Including:


Reducing Error:

• Errors can often be detected by making repeated measurements

• Error can be reduced by calibrating equipment

• The average or mean reduces data variations: it helps find a central value


• An accurate measurement is close to the true or correct value, a “hole-in-one”

• A precise measurement is close to the average of a series of repeated measurements

• When calibrated instruments are used properly, the greater the number of significant figures, the greater is the degree of precision for a given measurement

Accuracy vs. Precision


• Non-zero digits are significant

• Zeros between significant digits are significant

• Zeros to the right of non-zero digits in a number that contains a decimal point are significant (Trailing with a decimal point)

• Zeros to the left of the first nonzero digit are never counted as significant (Leading)

• Zeros at the end of a number without a decimal point are assumed not to be significant (Trailing without a decimal place)

Rules For Significant Figures (Sig Figs)


Learning Check: How Many Significant Figures Are There In The Following?

2.33 3

500.0 4

1000 1

.0500 3


Your Turn!

How many sig. figs. are there in the number 010.010?

A. 2

B. 3

C. 4

D. 5

E. none of these


Rules for combining measurements depend on the type of operation performed:

• Multiplication and division The number of sig. figs in the answer should not be

greater than the number of sig. figs in the factor with the fewest sig. figs

figs.) sig. (2

13

figs.) sig. (2figs.) sig. (4 figs.) sig. (3

0.642.751 3.14

Measurements Limit The Precision Of Calculated Results


Your Turn!

How many sig. figs. result from the following:

12.33 x 0.00002?

A. 2

B. 3

C. 4

D. 5

E. none of these

Only 1!


The answer should have the same number of decimal places as the quantity with the fewest number of decimal places (least precise)

3.247 ← 3 decimal places 41.36 ← 2 decimal places +125.2 ← 1 decimal place 169.8 ← answer rounded to 1 decimal place

Addition and Subtraction


Your Turn!

How many sig. figs. result from the following:

10.33-0.0344?

A. 2

B. 3

C. 4

D. 5

E. none of these


Exact Numbers

• Numbers that come from definitions are exact and have no uncertainty

• They can be assumed to contain an infinite number of significant figures


Your Turn!

How many sig. figs. result from the following?

A. 2

B. 3

C. 4

D. 5

E. none of these

2.2

12.2-10.88) x (10.0

1.7 Units can be converted using the factor-label method 60

Unit Conversions

• Suppose we wish to convert 25 miles to km. Further, we know that there are .6215 miles in a km.

• We can assemble a ratio and solve this problem.

easy enough because we have a direct conversion between the units

Often, we must piece together multiple steps and this approach is impractical

1km

miles 0.6215

km ?

miles 25


Definitions of One

• Remember that 3 teaspoons (tsp) = 1 tablespoon (Tbsp)

• Using the logic that a number divided by its equivalent = 1, then it follows that:

• Clearly 3/1 is not 1, but the units make the statement true.

• Thus we could multiply any number by either of these fractions (1) and the number has the same value.

13tsp

1Tbsp and 1

1Tbsp

3tsp


Learning CheckWrite two fractions from the following conversion factors

• 4 qt = 1 gal

• 8 fl oz=1 c

• 16 oz. = 1 lb

4 qt/ 1gal 1 gal/4 qt

8 fl oz / 1c and 1c/ 8 fl oz

16 oz./1 lb and 1 lb/16 oz.


Using Conversion Fractions

• Since we can multiply by “1” and the value remains unchanged, we can multiply by these conversion fractions to change the units of a measurement.

• For example, 12 in = 1 ft so the conversion of 3.5 ft to in. can be done using one of these two conversion fractions

1

5.3 ft

112in

1ft and 1

1ft

12in

inft

in42

1

12


Your Turn!

Given that 2.205 lb=1 kg, which of the following is an appropriate conversion factor?

kg 1

lb 1

kg 2.205

lb 2.205kg 1

lb 2.205

kg 2.205

lb 1 None of these

E.D.C.B.A.


USCS Unit Conversions

Mass Volume Distance16 oz. (avdp.) = 1 lb.2000 lb. = 1 T.

3 tsp. = 1 Tbsp.16 Tbsp. = 1 c.2 c. = 1 pt.2 pt. = 1 qt.4 qt. = 1 gal.8 fl. oz. = 1 c.

12 in. = 1 ft.3 ft. = 1 yd.1760 yd. = 1 mi.


USCS to Metric Metric to USCS Length 1 in. = 2.54 cm 1 m = 39.37 in

1 yd = 0.9144 m 1 km = 0.6215 mi1 mi = 1.609 km

Mass 1 lb = 453.6 g 1 kg = 2.205 lb1 oz = 28.35 g

Volume 1 gal = 3.785 L 1 L = 1.0567 qt1 qt = 946.4 mL1 oz (fluid) = 29.6 mL

It is also useful to know that 1 mL = 1 cm3=1 cc

USCS And Metric Units Are Related Using “Critical Links”


Building Conversion Factors in Unit Conversions

1. Write the number to be converted as a fraction (with units)

2. Identify the target units3. Are the starting units in the same system as the

target? If not, you will need a critical link. USCS→USCS Conversions: Write down the

conversion factors from smallest to largest . metric →metric conversions: Write down the

definitions of all prefixed units.


Learning Check:

Write all conversion factors needed to convert the following:

• 33 in to yd

• 450 c to gal

• 56 y to s

• 25 mph to ft/s

• 12 in.=1 ft• 3 ft =1 yd• 2 c.=1 pt.• 2 pt.=1 qt.• 4 qt.=1 gal.• 60 s=1 min• 60 min=1 h• 24 h=1 da• 365.25 da=1 y• Distance: 3 ft=1 yd; 1760 yd=1 mi• Time: 60 s=1 min; 60 min=1 h


Learning Check:

Write all conversion factors needed to convert the following:

• 33 mm to km

• 450 cg to ng

• 56 µs to Ms

• 25 mL to nL

• mm=10-3 m• km=103 m• cg=10-2 g• ng =10-9 g• μs=10-6 s• Ms=109 s• mL=10-3 m • nL=10-9 L


Learning Check:Write Down All Conversion Factors Needed To Convert

The Following:

• 3.03 g to T

• 0.545 ft to km

• 25 mph to km/s

•Crit. Link: 453.6 g=1 lb

•US→US: 2000 lb = 1 T

•CL: 2.54 cm=1 in

•US→US: 12 in=1 ft

•m→m: cm=10-2 m; km=103 m

•Distance: CL: 2.54 cm =1 in

•US→US 12 in = 1 ft; 3 ft= 1 yd; 1760 yd = 1 mi;

•m →m: cm = 10-2 m; km= 103 m

Time:

60 s=1 min

60 min= 1 h


Building Conversion factors (cont).

4. Use the form of the conversion factor that allows the units to cancel--they must be on opposite levels of the fraction to cancel.

5. Continue adding conversion factors until the units match the target units.

2nd Check- are all units written on the page two times? If so, you have enough info to start the problem.


Learning Check:

Convert the following:

• 3.03 g to tons

• 0.545 ft. to km

• 5.22 y to s

• 25 mph to km/s

•3.34(10-6) T

•1.66(10-4) km

•1.65(108) s

•1.1(10-2) km/s


Your Turn!

Given that 2.205 lb = 1 kg, what is the mass of 23.3 lb expressed in kg?

A. 51.4 kg

B. 0.0946 kg

C. 10.6 kg

D. none of these


Your Turn!

Given that 2.54 cm = 1 in, how many km are there in 25 ft?

A. 7.6 km

B. 0.10 km

C. 762 km

D. none of these 7.6(10-3) km!

1.8. Density is a useful intensive property 75

Density (d)

• intensive property defined as the ratio of an object’s mass (m) to volume (v), d = m/v

• characteristic of pure substances at a specified temperature

• Since most substances expand when heated, densities decrease when heated.

• units : g/L for gases and g/mL for solids and liquids.


Density relates a sample mass and volume

• Blood has a density of 1.05 g/cm3

• We can say that 1.05 g of blood is equivalent to 1.00cm3

• Conversion factors can be constructed from this equivalence, which could be used in the factor-label method

blood g 1.05

bloodcm 1.00or

bloodcm 1.00

blood g 1.05 3

3


Learning Check:

A crash sounds from the lab- a large vial of mercury has fallen from a broken shelf. We call the hazardous materials team to report the spill, about 2.0 quarts of mercury. They ask for the mass- what is it? (hint: d=13.69g/mL)

gmL

g

L

mL

qt

Lqt)10(6.2

69.13

100567.1

1

1

0.2 43

78

Your Turn!

A glass bead with a mass of 5.96 g is dropped into a beaker of water containing 10.2 mL. If the resulting volume is 12.3 mL, what is the density of the bead?

A. 2.1 mL

B. 5.96 g

C. 2.8 g/mL

D. 0.35 g/mL

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