chemistry: a science for the 21st centurypostonp/ch221/pdf/ch01-w20.pdf · 2020-02-20 · 2/20/2020...

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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

• Solar cells

• Quantum computers

• 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 Exploring the Particulate Nature of Matter

1.2 COAST: A Framework for Solving Problems

1.3 Classes and of Properties of Matter

1.4 The States of Matter

1.5 Forms of Energy

1.6 Formulas and Models

1.7 Expressing Experimental Results

1.8 Unit Conversions and Dimensional Analysis

1.9 Assessing and Expressing Precision and Accuracy

Chapter Outline

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Atoms and Atomism

FIGURE 1.1 Silicon wafers are

widely used to make computer

chips and photovoltaic cells for

solar panels. Scientists have been

able to image individual atoms

using an instrument called a

Scanning Tunneling Microscope

(STM). The radius of each atom is

117 picometers (pm), or 117

trillionths of a meter.

Atomic Theory: The Scientific Method in Action

A hypothesis is a tentative explanation for a set of observations

A theory is a tested explanation for a set of observations

A scientific law is the result of observing consistent patterns and relationships between physical phenomena.

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Early Chemical Discoveries (18th century)

Law of Definite Proportions (or Law of Constant Composition)– Joseph Louis Proust (1754-1826)

A compound always contains the same elemental composition by mass no matter what the source is.

e.g. 2 compounds containing Sn and O

21.2% O78.8% Sn

= 0.269

11.9% O88.1% Sn

= 0.135

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 Multiple Proportions – John Dalton (1766-1844)

e.g. 2 compounds containing Sn and O

21.2% O78.8% Sn

= 0.269

11.9% O88.1% Sn

= 0.135

0.269

0.135= 2

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• 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 → SO2

4.0 g 4.0 g 8.0 g

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

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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1.5 Forms of Energy





Chapter Outline

• 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 – A Framework for Solving Problems

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1.5 Forms of Energy





Chapter Outline

Matter - anything that occupies space and has mass.

Mass - defines the quantity of matter in an object.

Substance is a form of matter that has a definite composition and distinct properties = elements and compounds

Chemistry – the study of the composition, structure, and properties of matter and the changes it undergoes.

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PropertiesA way to describe matter based upon observations and measurements

Physical PropertiesProperties that can be measured or observed without changing the substance (melting point, temperature, density)

Chemical PropertiesProperty that describes how a substance will react; the substance will change into a new substance from this property (oxidation, flammability)

Na(s) + Cl2(g)

NaCl(s)

Extensive PropertiesDependent upon amount of substance (mass, length, volume)

Intensive PropertiesIndependent of the amount of substance present (color, odor, malleability, density, etc.)

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Practice 1.1 - Calculating DensityA metal coin is found on the beach. When taken into the laboratory it was found to have a mass of 3.90 grams. The diameter is 1.91 cm and its thickness is 0.150 cm. Using the values from the table in Practice Exercise 1.1 what is the likely composition of this coin?

What other information could be used to confirm the metal composition?

• Collect and Organize

• Analyze

• Solve

• Think About It

Collect and Organize• By comparing the density of the coin to the table of metal

densities we can determine the type of metal. The units for density are g/cm3. The volume of a coin (cylinder) is V = r2h.

Analyze

• Radius is one-half the diameter and the millimeters have to be converted to centimeters.

Solve

• Vcyl = r2h = p(0.955)2(0.150) = 0.430 cm3

• d = 𝑚

𝑉=

3.90 𝑔

0.430 𝑐𝑚3 = 9.07 g/cm3

• The coin is most likely copper but might be nickel.

• Color may help in determining the composition.

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Think About It

• Copper has a density of 9.0 g/cm3 and nickel has a density of 8.9 g/cm3. The color of copper is reddish-brown and nickel is gray. The color and density together would be used to determine the composition.

Molecules and Compounds• Compound

A compound is a pure substance made up of two or more different atom types held together by a chemical bond.

• Chemical bond

A chemical bond is a force that holds atoms together.

• Molecule

Groups of atoms with no charge

• Ions

Atoms that have a positive or negative charge

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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

24 elements have been created by scientists

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

http://www.webelements.com/

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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httphttps://www.webelements.com/

http://www.webelements.com/

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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.

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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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1.5 Forms of Energy





Chapter Outline

•solid = definite volume and shape

•gas = indefinite volume and shape

•liquid = definite volume, indefinite shape

States of Matter

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1.5 Forms of Energy





Chapter Outline

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https://tinyurl.com/clj7f7u

QR Code Reader and Scanner 4+ShopSavvy, Inc.

Bar Code Reader App (IOS)

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

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

Kinetic Energy (KE) = energy of motion

KE = ½ mv2 m = mass

v = velocity

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Energy of position or stored energy

PE = mgh

m = mass

g = gravitational constant

h = height

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

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1.5 Forms of Energy





Chapter Outline

Chemistry: An Atoms-Focused Approach, 2nd Edition Copyright © 2017, W. W. Norton & Company

Formulas and Models

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.

o Molecular formulas

o Structural formulas

o Condensed structural formulas

o Ball-and-stick models

o Space-filling models

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Ball and Stick and Space-Filling Models


Molecular and Structural Formulas

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1.5 Forms of Energy





Chapter Outline

The Metric SystemNational Institute Science & Technology

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The Metric (SI) System

◼ SI Units (Systéme International d’Unites)

◼ Base Units - meter, kilogram, second, Kelvins, etc

◼ All other units are derived from the base units, e.g. force in Newtons = kg/ms2, velocity = m/s, frequency = oscillations per second, or s-1 (Hertz or Hz)

◼ Everything is based on powers of 10

◼ We can change the size of the base units by adding prefixes

e.g. 1 meter = 102 centimeters or1 m = 100 cm

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◼ 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

◼ there is a modern definition based on the speed of light.

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

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

Length - Base Unit is the meter (m)


Mass - Base Unit is the Kilogram (kg)

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

• modern definition is based on what is known as “Planck’s Constant”.

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Volume – Derived Base Unit is the liter (L)

◼ Derived from units of length

◼ 1 Liter = cube 10 cm on a side = 1000 cm3

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


Converting Units Within the Metric System

(a) 10,100 g to kg

(b) 50 mL to liters

(c) 16.5 cm to mm

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There are 9 oF for every 5 oC and K = C + 273

(MEMORIZE!)

Section 1.10 - Temperature Scales

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?

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Numbers & Scientific Measurements

• Accuracy = closeness to the true or

accepted value

• Precision = the reproducibility of the

measurement

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Significant FiguresDigits in a measurement which are known with

certainty, plus a last digit which is estimated

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 =

e.g. 0.000592 =

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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 is it 1, 2 or 3 sig figs?)

• Leading zeros are not significant. They simply locate the decimal point (.00002)

Exact Numbers – no uncertainty in the number of sig fig’s; based on counting or definitions

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

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

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◼ Multiplication/Division

12.154

5.23

36462

24308

60770

63.56542

Rule: Look at the numbers involved in the calculation, find the number with the fewest number of sig figs, and round the answer off to the same number of sig figs

ans = 63.6

Reporting the Correct # of Sig Fig’s

Reporting the Correct # of Sig Fig’s

⚫ Addition/Subtraction

15.02

9,986.0

3.518

Rule: find the number that has an uncertain digit closest to the decimal point, and then round off the answer to that decimal point.

10004.538

ans = 10004.5

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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

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 = 2.91.12

sig figs ? 5 sig figs

3 sig figs

If you round off too soon you create a rounding error:

0.22 x 15.239 = 2.993375 = 3.01.12

1.235-1.02

0.215 = 0.22

rounding off at the end

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1.5 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 cm X 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

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

• Converting a value from one unit to another:

Unit Conversions and Dimensional Analysis; Conversion Factors

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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!

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chemistry: a science for the 21st centurypostonp/ch221/pdf/ch01-w20.pdf · 2020-02-20 · 2/20/2020...

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