chemistry: a science for the 21st centurypostonp/ch221/pdf/ch01-w14.pdf · 2018. 1. 19. ·...

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Chemistry: A Science for the 21st Century

• HEALTH AND MEDICINE

• Human Genome Project

• New cancer treatments

• Vaccines and antibiotics

•ENERGY

• Fuel Cells

• Solar energy

• Nuclear energy

Chemistry: A Science for the 21st Century

• MATERIALS AND TECHNOLOGY

• Polymers, ceramics, liquid crystals

• Room-temperature superconductors

• Molecular computing

• FOOD AND AGRICULTURE

• Genetically modified crops

• “Natural” pesticides

• Specialized fertilizers

• Green chemistry

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Students

Biologists

•cells and cell

membranes

•nucleus and

mitochondria

•DNA, RNA

•Metabolism, e.g.

free energy ATP

production

Geologists

•Minerals, crystal

lattices

•silicate minerals,

building blocks of

rocks

•Geochemistry, e.g.

radioactive

groundwater plumes

at Hanford

•evaporites

(precipitates)

Chemists

•synthesize new

materials, drugs,

products

•control reactions

•Analyze the

concentrations of

samples

•Identify unknowns

Professional Careers – it’s time to get serious now! Your degree shows

an employer that you are able to accomplish a goal, overcome obstacles,

apply creative problem solving, work in a team, and effectively

communicate in both verbal and written formats.

http://hubblesite.org/gallery/album/pr2001009b/

Nucleosynthesis and the Origin of the Elements

•Big Bang Nucleosynthesis = mainly H and He

•Stellar Nucleosynthesis = elements up to Fe formed within stars

•Supernova = produces heaviest elements and disseminates all

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1.1 States of Matter

1.2 Forms of Energy

1.3 Classes of Matter

1.4 Properties of Matter

1.5 Atomic Theory: The Scientific Method in Action

1.6 A Molecular View

1.7 COAST: A Framework for Solving Problems

1.8 Making Measurements and Expressing Results

1.9 Unit Conversions and Dimensional Analysis

1.10 Temperature Scales

Chapter Outline

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1. Matter - anything that occupies space and has

mass.

2. Mass - defines the quantity of matter in an object.

3. Substance is a form of matter that has a definite

composition and distinct properties.

4. Energy – capacity to do work

Chemistry – the study of the composition, structure, and properties of matter and of the energy consumed or given off when matter undergoes a change

Sec. 1.1 - States of Matter

•solid = definite volume and shape

•gas = indefinite volume and shape

•liquid = definite volume, indefinite shape

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1.2 Forms of Energy









Chapter Outline

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Work, Potential and Kinetic Energy

ENERGY is the capacity to perform WORK

WORK is a force over a distance (F x d)

An object can possess energy in only two

ways, (1) kinetic and (2) potential energy

from Paul A. Tipler and Gene Mosca, "Physics for Scientists and Engineers", Fifth Edition, 2003, W. H. Freeman & Company

from Paul A. Tipler and Gene Mosca, "Physics for Scientists and Engineers", Fifth Edition, 2003, W. H. Freeman & Company

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Kinetic Energy (KE) = energy of motion

KE = ½ mv2 m = mass

v = velocity

Energy of position or stored energy

PE = mgh

m = mass

g = gravitational constant

h = height

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Law of Conservation of Energy

“Energy can neither be created or destroyed,

just changed from one form to another”

FORMS

•radiant (light)

•thermal (heat)

•chemical

•electrical

•mechanical

ENERGY

the capacity to

do work

TYPES OF

ENERGY

•potential

•kinetic


1.2 Forms of Energy









Chapter Outline

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Section 1.3 - Classes of Matter

An element is a substance that cannot be

separated into simpler substances by chemical

means.

• 118 elements have been identified

• the first 94 elements occur naturally on Earth

gold (Au), aluminum (Al), lead (Pb), oxygen (O2), carbon (C)

• elements after #83 (Bi) are all radioactive

28 elements have been created by scientists

technetium (Tc), americium (Am), seaborgium(Sg), etc

http://www.webelements.com/

http://www.webelements.com/

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MEMORIZE the names and symbols of the first 38 elements PLUS Ba,Pb, Sn, Ag, Cd, Hg, Au, I, Xe, U

As

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A compound is a substance composed of atoms

of two or more elements chemically united in fixed

proportions.

Compounds can only be separated into their

pure components (elements) by chemical

means.

Law of Constant Composition

• All samples of a particular compound contain the same elements combined in the same proportions.

• Example: water (H2O)

Consists of two units of hydrogen (H) combined with one unit of oxygen (O)

Elements and proportions represented by chemical formula

Compounds, cont’d

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1. Homogeneous

▪ also known as solutions, its components are

distributed uniformly throughout the sample and have

no visible boundaries or regions.

Mixtures

2. Heterogeneous

▪ components are not distributed uniformly, contains

distinct regions of different compositions

Mixtures

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Separating Mixtures

Distillation

Distillation

Lab distillation apparatus

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Filtration

Chromtography

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1.2 Forms of Energy









Chapter Outline

Sec. 1.4 - Properties of Matter

Intensive property:

• Independent of the amount of substance present.

• Examples: color, hardness, density (d = mass/volume).

Extensive property:

• Varies with the quantity of the substance present.

• Examples: volume, mass, etc.

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Physical properties: • Characteristics of a substance that can be

observed without it changing into another substance.

• Examples: luster, hardness, color, etc.

Chemical properties:• Characteristics that can be observed only

when a substance reacts with another substance.

• Examples: Carbonates produce a gas when added to acidic solutions.

Properties of Matter, cont’d


1.2 Forms of Energy









Chapter Outline

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1.Observations

2.Hypothesis

3.Prediction

4.Experiment

The Scientific Method is a systematic approach to research

A hypothesis is a tentative explanation for a set of observations

Theory

A theory is a tested explanation for a set of observations

A law is a concise statement of a relationship between phenomena that is always the same under the same conditions.

Early Chemical Discoveries (18th century)

• Law of Definite Proportions –

different samples of the same compound always contain the same elements in the same proportion by mass

2 HgO → 2 Hg + O2

50.0 g 46.3 g 3.7 g

% O = 3.7/50 x 100% = 7.4%

% Hg = 46.3/50 x 100% = 92.6%

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Law of Multiple Proportions –

When two elements combine to make two (or more) different compounds, the mass ratio of the two elements in the first compound, when divided by the mass ratio for the second compound, form simple whole number ratios (e.g. 3/2, 4/1 etc).

• Law of Conservation of Mass –

(Antoine Lavoisier, 1743-1794) - the mass of substances present after a chemical reaction is equal to the mass of the substances entering into the reaction (mass reactants = mass products)

S + O2 → SO24.0 g 4.0 g 8.0 g

http://en.wikipedia.org/wiki/Antoine_Lavoisier

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Law of Conservation of Mass

DALTON’S ATOMIC THEORY

1. Elements are composed of extremely smallparticles called ATOMS. All atoms of a given element are identical, having the same size, mass, and chemical properties. The atoms of one element are different from the atoms of all other elements.

2. Compounds are composed of atoms of more than one element. In any compound, the ratio of numbers of atoms of any two of the elements present is either an integer or a simple fraction (Law of Definite Proportions, Law of Multiple Proportions)

3. A chemical reaction involves only the separation, combination, or rearrangement of atoms; it does not result in their creation or destruction (Law of Conservation of Mass)

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1.2 Forms of Energy









Chapter Outline

A Molecular View

Chemical Formula

• Notation for representing elements and compounds

• Consists of symbols of constituent elements, and subscripts identifying the number of atoms of each element in one molecule.

Molecular Formula

Structural Formula

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Chemical bonds link atoms together to make molecules.

Chemical formulas can be represented in four ways:

• Molecular formulas • Structural formulas• Condensed structural

formulaso Ball-and-stick

modelso Space-filling models

Chemical Formulas


1.2 Forms of Energy









Chapter Outline

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Collect and Organize• Identify key concepts, skills required to

solve problem, and assemble information

needed.

Analyze• Evaluate information and relationships or

connections; sometimes units will help identify steps needed to solve the problem.

Solve• Perform calculations, check units, etc.

Think about it• Is the answer reasonable? Are the units

correct?

COAST


1.2 Forms of Energy









Chapter Outline

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The Metric (SI) System

SI Units (Systéme International d’Unites)

Sometimes referred to as MKS units (meter, kilgram, second)

All other units are derived from BASE UNITS

Everything is based on powers of 10

We can change the size of the base units by changing prefixes

e.g. 1 meter = 100 centimeters

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Length - Base Unit is the meter (m)

In 1791, soon after the French Revolution, the French Academy of Sciences defined the meter as equal to 10-7 or one ten-millionth of the length of the meridian through Paris from pole to the equator.

kilometer =

centimeter =

nanometer =

picometer =

http://physics.nist.gov/cuu/Images/alloy1874.jpeg

http://www.lightandmatter.com/html_books/1np/ch00/figs/france.png

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Volume – Derived Base Unit is the liter (L)

Derived from units of length

cube 1 dm on a side

a milliliter (mL) = 1 cubic centimeter (cc)

Mass - Base Unit is the kilogram

kilogram =

milligram =

microgram =

http://physics.nist.gov/cuu/Units/kilogram.html

Originally a kilogram was the mass of a cubic decimeter of water at its temperature of maximum density. In 1889 it was changed to a “prototype” made of a platinum-iridium alloy.

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Scientific Notation

A way to write any number in a format

consisting of a number between 1 and 10,

multiplied by a power of 10 (N x 10n)

e.g. 125,817. = 1.25817 x 105

e.g. 0.000592 = 5.92 x 10-4.

.

Converting Units Within the Metric System

(a) 10,100 g to kg

(b) 1.35 m to cm

(c) 50 mL to liters

(d) 16.5 cm to mm

(e) 104 m to nm

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Numbers & Scientific Measurements

Accuracy = closeness to the true or accepted value

Precision = the reproducibility of the measurement

Significant Figures

Digits in a measurement which are known with certainty, plus a last digit which is estimated

beakerburet

graduated cylinder

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Rules for Determining How Many Significant Figures There are in a Number

• All nonzero digits are significant (4.006, 12.012, 10.070)

• Interior zeros are significant (4.006, 12.012, 10.070)

• Trailing zeros FOLLOWING a decimal point are significant (10.070)

• Trailing zeros PRECEEDING an assumed decimal point may or may not be significant (500 – 1, 2 or 3 sig figs?)

• Leading zeros are not significant. They simply locate the decimal point(0.00002)

Sample Exercise 1.2

Which of the following numerical values associated with the Washington Monument in Washington, DC, are exact numbers and which are not exact? (a) the monument is made of 36,491 white marble blocks; (b) the monument is 169 m tall; (c) there are 893 steps to the top; (d) the mass of the aluminum capstone is 2.8 kg; (e) the area of the foundation is 1487 m2

Exact Numbers – no uncertainty in the

number of sig fig’s; based on counting

or definitions

e.g. 1 meter/100 cm; 5 nickels

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Reporting the Correct # of Sig Fig’s

Multiplication/Division

12.154

5.23Rule: Round off to the fewest number of sig figs in the calculation

36462

24308

60770

63.56542

ans = 63.6

Reporting the Correct # of Sig Fig’s

Addition/Subtraction

15.02

9,986.0

3.518

Rule: Round off to the least precise decimal place

10004.538

ans = 10004.5

9,986.0

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Rounding Off Rules

digit to be dropped > 5, round UP158.7 = 159

digit to be dropped < 5, round DOWN158.4 = 158

digit to be dropped = 5, round so the result is EVEN

158.5 = 158.0 157.5 = 158.0

BUT 158.501 = 159.0 (be careful –look at all the digits)

When Do You Round Off ?

Wait until the END of a calculation in order to avoid a “rounding error”

(1.235 - 1.02) x 15.239 = 2.923438 =1.12

1.235-1.02

0.215 = 0.22

? sig figs 5 sig figs

3 sig figs

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1.2 Forms of Energy









Chapter Outline

Problem-Solving by Dimensional Analysis

Rule: When multiplying or dividing numbers, we do the same thing to the units, for example -

If the dimensions are 10 cm X 30 cmX 20 cm, then the volume = 6,000 cm3

If you drive 120 miles in 2.0 hours then your average speed = 120 miles/2.0 hrs = 60 mi/hr

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Conversion factors

• e.g. 1 km = 0.6214 mi

Converting a value from one unit to another:

Changing Units: Conversion Factors

You can arrange the numerator and denominator as needed:

e.g. convert 4.5 mi to km:

e.g. convert 2.98 km to mi

Section 1.9 – Unit Conversions and Dimensional Analysis;

Conversion Factors

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Example similar to p. 22

A nugget of a shiny yellow mineral has a mass of 30.01 g. Its volume is determined by placing it in a 100 mL graduated cylinder containing 56.3 mL of water. The volume after the nugget is added is 62.6 mL. Is the nugget made of gold? The density of gold is 19.3 g/mL.

Sample Exercise 1.4

Converting between Metric and English Units

On April 12, 1934, a wind gust of 231 miles per hour was recorded at the summit of Mount Washington in New Hampshire. What is this wind speed in meters per second?

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Convert 6.75 ft to m

(1 in = 2.54 cm exactly)

Convert 65 mi/hr to m/s

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2 and 3-D Conversions

Do not forget to square or cube the number if you have to square or cube the unit!

e.g. convert 4.0 m2 to ft2

Using Percent as a Conversion Factor

Battery plates in lead storage batteries are made from a mixture of lead (94.0%) and antimony (6.0%). If a piece of battery plate has a mass of 25.0 g, what masses of lead and antimony are present?

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1.2 Forms of Energy









Chapter Outline

There are 9 oF for every 5 oC and K = C + 273 (MEMORIZE!)

Section 1.10 - Temperature Scales

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Practice: Temperature Conversions

The lowest temperature measured on the Earth is −128.6°F, recorded at Vostok, Antarctica, in July 1983. What is this temperature in °C and in Kelvin?

chemistry: a science for the 21st centurypostonp/ch221/pdf/ch01-w14.pdf · 2018. 1. 19. ·...

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