chapter 1 chemistry and chemicals student

7/28/2019 Chapter 1 Chemistry and Chemicals Student

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General, Organic, and

Biological ChemistryFourth Edition

Karen Timberlake

Welcome to

Chemistry 121

2013 Pearson Education, Inc.


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Karen Timberlake

Chapter 1

Chemistry andMeasurements

2013 Pearson Education, Inc.Lectures


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2013 Pearson Education, Inc. Chapter 1, Section 1 3

What is Chemistry?

Chemistry is the study of matter and its composition,

structure,

properties, and

reactions

Chemsitry occurs all around you, for example,

when you

cook food,

add chlorine to your pool,

digest food, and

drop an antacid tablet in a glass of water.


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Success in Chemistry 121

Regular attendance, active participation in

problem solving

Ask questions early and often!

Seek extra help as needed show up beforeclass, take advantage to tutoring sessions

Follow the suggestions given in chapter one

of the text book, learn how to use the differentfeatures of your text book

4


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Using your textbook

Before reading, review topics in Looking Ahead.

Review Learning Goals at the beginning of each

section. Solve Concept Checks to help you understand

the key ideas in each chapter.

After reading, work through Sample Problems

and try the associated Study Checks. Work the sets ofQuestions and Problems at the

end of each section.


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Active Learning

Use Active Learning methods to help you learn chemistry.

Read all assigned materials before you attend lectures.

Note questions you have about the reading to discusswith your instructor

Practice problem solving.

Attend the office hours for help.


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Form a Study Plan





Karen Timberlake

Chapter 1

Chemistry and

Measurements

2013 Pearson Education, Inc.



Sec. 1.3 Measurement in Science

walking 2.1 km to campus,

carrying a backpack with a mass of 12 kg, and

observing when the outside temperature has reached22 oC.

Notice that all measurements have 2 components

A numerical value

A unit written after the numerical value, to indicate thetype of measurement made.

We use measurements in everyday life, such as



Units of Measurement:

The Metric and SI Systems

The metric system and SI (Systme International)

are used

for length, volume, mass, temperature, and time,

in most of the world, and everywhere by scientists.



Units in the Metric System

In the metric and SI systems, one unit is used for each

type of measurement.

Measurement Metric Base Unit SI UnitLength meter (m) meter (m)

Volume liter (L) cubic meter (m3)

Mass gram (g) kilogram (kg)

Temperature Celsius (C) Kelvin (K)

Time second (s) second (s)



Length Measurement

Length

uses the unit meter

(m) in both the metric

and SI systems. uses centimeters (cm)

for smaller units of

length.

The letter c in front ofthe m is called a

metric prefix and

denotes a specific

power of 10



Converting Between Different Units

of Length -- Inches, Centimeters, and

Meters

Useful relationships between units of length



Volume Measurement

Volume

is the space occupied by a

substance.

uses the unit liter (L) in themetric system.

uses the unit cubic meter

(m3

) in the SI system. is measured using a

graduated cylinder in units

ofmilliliters (mL).



Converting between Quarts,

Liters, and Milliliters

Useful relationships between units of volume



Mass Measurement

The mass of an object is

a measure of the quantity

of material it contains.

measured in grams (g) forsmall masses.

is measured in kilograms

(kg) in the SI system.

The standard kilogram for

the United States is stored at

the National Institute of

Standards and Technology.



Converting Between Pounds,

Grams, and Kilograms

Useful relationships between units of mass



Temperature Measurement

measured on the Celsius

(C) scale in the metric

system,

measured on the Kelvin (K)

scale in the SI system, and

18C or 64F on this

thermometer.

Temperature indicates how hot or cold a substance

is, and is



Section 1.4 Scientific Notation

Scientific Notation

is used to write very large

or very small numbers.

is used to give the widthof a human hair (0.000

008 m) as

8 x 10-6 m.

for a large number suchas 100 000 hairs is written

as

1 x 105 hairs.



Writing Numbers in Scientific

Notation

A number in scientific notation contains a coefficient

between 1 and 10 and a power of 10 and a unit.

When converting a number from standard notation to

scientific notation, the decimal point is moved until

there is only be one digit to the left of the decimal point

For numbers larger than 1, the power of 10 is positive.

For numbers less than 1, the power of 10 is negative

0.0075 L = 7.5 x 0.001 = 7.5 x 10-3 L



Some Powers of Ten



Scientific Notation and

Calculators

You can enter a number in scientific notation on

many calculators using the EE or EXP key.

Use the (+/) key to change the value of theexponent from positive to negative.


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Calculators

You can enter a number in scientific notation on

many calculators using the EE or EXP key.

Use the (+/) key to change the value of the

exponent from positive to negative.


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Calculators

When a calculator display appears in scientific notation,

it is shown as a number between 1 and 10 followed by a

space and the power of 10.


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Calculators

To write this number in correct scientific notation, write

the coefficient and use the power of 10 as an exponent.


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Converting Scientific Notation to a

Standard Number

When a number in scientific notation has a positive

power of 10,

move the decimal point to the right for the same

number of places as the power of 10 and

add placeholder zeros to give the additional decimal

places needed.


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Converting Scientific Notation to a

Standard Number

When a number in scientific notation has a negative

power of 10,

move the decimal point to the left for the same

number of places as the power of 10 and

add placeholder zeros in front of the coefficient as

needed.


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Karen Timberlake

1.5

Measured Numbers andSignificant Figures

Chapter 1




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Representing Measured Numbers

Measured numbers are numbers obtained by using

measuring devices, such as

a scale or analytical balance,

a graduated cylinder,

a clock or stopwatch, or

a ruler

Section 1.5 Measured Numbers and

Significant Figures


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Writing down measured numbers

Make sure you write down all numbers in the

measurement and include the measurement unit

The number of digits you record will depend on the

sentsitivity of the measuring device being used

For example, on a metric ruler with lines marking

divisions of 0.1cm, write the length to 0.1 cm and

estimate the value of the final number to 0.01 cm by

visual inspection (you can estimate one decimal

place beyond the smallest increments on the

measuring deviceThe length of the

wood shown to

the left would be

written down as

4.55 cm


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The Concept of Significant Figures

When making a measurement, the number ofdigits written down include all the digits you are

certain of plus the first estimated digit.

A number is a significant figure if it is a nonzero number. (234 g, 3 SF)

a zero between nonzero numbers.

(50071 g, 5 SF)

a zero at the end of a decimal number.(50.00 m, 4 SF)

the coefficient of a number is written in

scientific notation. (2.0 x 103 m, 2 SF)


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The Atlantic-Pacific Rule For Significant Digits

Imagine your number in the middle of thecountry

Pacific Atlantic

If a decimal point is present, start counting

digits from the Pacif ic(left) side of the

number, The first sig fig is the first nonzero digit, then

any digit after that.

e.g. 0.003100 would have 4 sig figs


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The Atlantic-Pacific Rule For Significant Digits

Imagine your number in the middle of thecountry

Pacific Atlantic

If the decimal point is absent, start counting

digits from the Atlantic (right) side, starting

with the first non-zero digit. The first sig fig isthe first nonzero digit, then any digit after that

e.g. 31,400 ( 3 sig. figs.)


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Scientific Notation and Significant

Zeros

When one or more zeros in a large number are

significant, they are shown more clearly by writing the

number in scientific notation.

5,000. kg 5.000 x 103 kg

If zeros are not significant, we use only the nonzero

numbers in the coefficient.

5,000 kg 5 x 103 kg


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Exact Numbers

Exact numbers are

those numbers obtained by counting items.

those numbers in a definition comparing two units

in the same measuring system. not measured and do not affect the number of

significant figures in a calculated answer.


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Karen Timberlake

1.6

Significant Figures inCalculations

Chapter 1




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Sec. 1.6 Mathematical Calculations

and Significant Figures

The number of significant

figures in measured

numbers are used to limit

the number of significant

figures in the final answer.

Calculators do not provide

the appropriate number of

significant figures.


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Rounding Off

To represent the appropriate number of significant

figures, we use "rules for rounding."

1. If the first digit to be dropped is 4 or less, then it, and

all following digits are simply dropped from thenumber.

2. If the first digit to be dropped is 5or greater, then the

last retained digit of the number is increased by 1.


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Rounding Off


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When multiplying or dividing use

the same number of significant figures (SF) as the

measurement with the fewest significant figures, and

the rounding rules to obtain the correct number ofsignificant figures.

Multiplication and Division


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When multiplying or dividing use

the same number of significant figures (SF) as the

measurement with the fewest significant figures, and

the rounding rules to obtain the correct number ofsignificant figures.

Multiplication and Division


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Sometimes we add one or more significant zeros to

the calculator display in order to obtain the correct

number of significant figures needed.

Example:

Suppose the calculator display is 4, and you need

3 significant figures.

4 becomes 4.00

1 SF 3 SF

Adding Significant Zeros


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When adding or subtracting, use

the same number of decimal places as the

measurement with the fewest decimal places and

the rounding rules to adjust the number of digits inthe answer.

one decimal place

two decimal places

calculated answerfinal answer (with one

decimal place)

Addition and Subtraction


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Sec. 1.7 Metric Prefixes and Equalities

A prefix in front of a unit increases or decreases the size of that

unit.

makes units larger or smaller than the initial unit by one

or more factors of 10. indicates a numerical value.


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Metric and SI Prefixes

Prefixes that increase the size of the unit:


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Metric and SI Prefixes

Prefixes that decrease the size of the unit:


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Daily Values for Selected Nutrients


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An equality

states the same measurement in two different units.

can be written using the relationships between two

metric units.

Example: 1 meter is the same as 100 cm and 1000 mm.

Metric Equalities


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Measuring Length

The metric length of 1 meter is the same length as 10 dm, 100 cm,

and 1000 mm.

Q How many millimeters (mm) are in 1 centimeter (cm)?


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Measuring Volume


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Measuring Mass

Several equalities can be written for mass in

the metric (SI) system.

S 1 8 S l i P bl I Ch it


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Sec. 1.8 Solving Problems In Chemsitry

Using Dimensional Analysis and Conversion

Factors Dimensional Analysis is a problem-solving

method used in science

It depends on your ability to identify the

numerical information given by the problem,

and your ability to identify the numerical

information you are supposed to find when

solving the problem. The link between the known value (given)

and the unkown value (find) is called a

Converion Factor

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Equalities

use two different units to describe the same measured

amount.

are written for relationships between units of the metric

system; between U.S. units or between metric and

U.S. units.

Examples:

Equalities


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Equalities are

written as a fraction.

used as conversion factors.

can be represented with one equality in the numeratorand the second equality in the denominator.

Examples:

Equalities and Conversion Factors


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Common Equalities

E t d M d N b


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Exact and Measured Numbers

in Equalities

Equalities between units of

the same system are definitions with numbers that

are exact.

differentsystems (metric and U.S.) are

measurements with numbers that have significant

figures.

The equality of 2.54 cm = 1 in. is an exception and

considered to be exact.


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Metric Conversion Factors

We can write equalities as conversion factors.


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MetricUS conversion factors are written as a ratio with

a numerator and denominator.

Example:

Metric-US Conversion Factors


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Equalities on Food Labels

The contents of packaged foods

in the U.S. are listed in both metric and U.S. units.

indicate the same amount of a substance in two

different units.


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A percent factor

uses a ratio of the parts to the whole in a fraction.

uses the same units for the parts and whole.

uses the value 100 for the whole.

can be written as two factors.

Example:A food contains 18% (by mass) fat.

Percent as a Conversion Factor

G l O i d


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Karen Timberlake

1.9

Problem Solving

Chapter 1



Guide to Problem Solving Using


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There are 4 steps to solving problems with conversion

factors.

Guide to Problem Solving Using

Conversion Factors


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If a person weighs 164 lb, what is the body mass inkilograms?

Step 1 State the given and needed quantities.Analyze the Problem

Step 2 Write a plan to convert the given unit to the

needed unit.

lb USMetric kilogramsFactor

Steps to Solving the Problem

Given Need

164 lb kilograms


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If a person weighs 164 lb, what is the body mass in

kilograms?

Step 3 State the equalities and conversion

factors.

Step 4 Set up the problem to cancel units and

calculate the answer.



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If a person weighs 164 lb, what is the body mass in

kilograms?

Step 3 State the equalities and conversion

factors.

Step 4 Set up the problem to cancel units and

calculate the answer.



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Often, two or more conversion factors are required to

obtain the unit needed for the answer.

Unit 1 Unit 2 Unit 3

Additional conversion factors are placed in the setup

to cancel each preceding unit.

Using Two or More Factors


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How many minutes are in 1.6 days?

Step 1 State the given and needed quantities.

Analyze the Problem.

Step 2 Write a plan to convert the given unit to the

needed unit.days time time min

factor 1 factor 2

Example: Problem Solving

Given Need

1.6 days minutes


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How many minutes are in 1.6 days?

Step 3 State the equalities and conversion factors.

Step 4 Set up problem to cancel units and

calculate answer.

Example: Problem Solving


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Density

compares the mass of an object to its volume.

is the mass of a substance divided by its volume.

are measured in g/L for gases.

are measured in g/cm3 or g/mL for solids and liquids.

Density expression:

Density

General Organic and


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Karen Timberlake

1.10

Density

Chapter 1




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Density

compares the mass of an object to its volume.

is the mass of a substance divided by its volume.

are measured in g/L for gases.

are measured in g/cm3 or g/mL for solids and liquids.

Density expression:

Density


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Densities of Common Substances


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Density Calculations


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Calculating Density

If a 0.258-g sample of HDL has a volume of 0.215 cm3,

what is the density, in g/cm3, of the HDL sample?

Step 1 State the given and needed quantities.

Analyze the Problem.

Step 2 Write the density expression.

Given Need

0.258 g HDL

0.215 cm3 HDL

density in g/cm3 of HDL


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Calculating Density

If a 0.258-g sample of HDL has a volume of 0.215 cm3

,what is the density, in g/cm3, of the HDL sample?

Step 3 Express mass in grams and volume in

milliliters (mL) or cm3

.

Step 4 Substitute mass and volume into the density

expression and calculate the density.


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Sink or Float

Ice floats in water because the density of ice is less than

the density of water.

Aluminum sinks in water because its density is greater

than the density of water.


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Density can be written as a conversion factor.

Problem Solving using Density


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Density can be used as a conversion factor.

A density of 3.8 g/mL, can be written as an equality,

or written as conversion factors.

Problem Solving using Density

Problem: Density as a Conversion


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Factor

If the density of milk is 1.04 g/mL, how many grams of

milk are in 0.50 qt of milk?

Step 1 State the given and needed quantities.Analyze the Problem.



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Factor



Step 1 State the given and needed quantities.Analyze the Problem.



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Factor



Step 2 Write a plan to calculate needed quantity.

volume USMetric density mass

factor factor

Step 3 Write equalities and conversion factors.

Problem: Density as a


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Problem: Density as a

Conversion Factor



Step 4 Set up the problem to calculate the needed

quantity.

S ifi G i


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Specific Gravity (sp gr)

is the relationship between the density of a

substance and the density of water.

is determined by dividing the density of the sample

by the density of water.

is a unitless quantity.

Specific Gravity

S ifi G i


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Specific Gravity is measured by an instrument called

a hydrometer.

Specific Gravity

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